Fixed most small problems reported by cppcheck for src/core

The following command was used:
```
cppcheck \
	--verbose --quiet --error-exitcode=1 --force \
	--enable=warning,style,performance,portability \
	src/core/
```

src/core/android/SDL_android.c

@@ -766,10 +766,10 @@ JNIEXPORT int JNICALL SDL_JAVA_INTERFACE(nativeRunMain)(JNIEnv *env, jclass cls,
              */
             argv[argc++] = SDL_strdup("app_process");
             for (i = 0; i < len; ++i) {
-                const char *utf;
                 char *arg = NULL;
                 jstring string = (*env)->GetObjectArrayElement(env, array, i);
                 if (string) {
+                    const char *utf;
                     utf = (*env)->GetStringUTFChars(env, string, 0);
                     if (utf) {
                         arg = SDL_strdup(utf);
@@ -1420,10 +1420,10 @@ SDL_bool Android_JNI_ShouldMinimizeOnFocusLoss()
 
 SDL_bool Android_JNI_GetAccelerometerValues(float values[3])
 {
-    int i;
     SDL_bool retval = SDL_FALSE;
 
     if (bHasNewData) {
+        int i;
         for (i = 0; i < 3; ++i) {
             values[i] = fLastAccelerometer[i];
         }

src/core/freebsd/SDL_evdev_kbd_freebsd.c

@@ -136,7 +136,7 @@ static void kbd_cleanup_signal_action(int signum, siginfo_t* info, void* ucontex
 
 static void kbd_unregister_emerg_cleanup()
 {
-    int tabidx, signum;
+    int tabidx;
 
     kbd_cleanup_state = NULL;
 
@@ -146,6 +146,7 @@ static void kbd_unregister_emerg_cleanup()
     kbd_cleanup_sigactions_installed = 0;
 
     for (tabidx = 0; tabidx < sizeof(fatal_signals) / sizeof(fatal_signals[0]); ++tabidx) {
+        int signum;
         struct sigaction* old_action_p;
         struct sigaction cur_action;
         signum = fatal_signals[tabidx];
@@ -176,7 +177,7 @@ static void kbd_cleanup_atexit(void)
 
 static void kbd_register_emerg_cleanup(SDL_EVDEV_keyboard_state * kbd)
 {
-    int tabidx, signum;
+    int tabidx;
 
     if (kbd_cleanup_state != NULL) {
         return;
@@ -198,6 +199,7 @@ static void kbd_register_emerg_cleanup(SDL_EVDEV_keyboard_state * kbd)
     kbd_cleanup_sigactions_installed = 1;
 
     for (tabidx = 0; tabidx < sizeof(fatal_signals) / sizeof(fatal_signals[0]); ++tabidx) {
+        int signum;
         struct sigaction* old_action_p;
         struct sigaction new_action;
         signum = fatal_signals[tabidx];   
@@ -475,12 +477,12 @@ SDL_EVDEV_kbd_keycode(SDL_EVDEV_keyboard_state *kbd, unsigned int keycode, int d
     unsigned int final_key_state;
     unsigned int map_from_key_sym;
 
-    key_map = *kbd->key_map;
-
     if (!kbd) {
         return;
     }
 
+    key_map = *kbd->key_map;
+
     kbd->rep = (down == 2);
 
     if (keycode < NUM_KEYS) {

src/core/linux/SDL_evdev.c

@@ -767,7 +767,6 @@ SDL_EVDEV_sync_device(SDL_evdevlist_item *item)
 static int
 SDL_EVDEV_device_added(const char *dev_path, int udev_class)
 {
-    int ret;
     SDL_evdevlist_item *item;
     unsigned long relbit[NBITS(REL_MAX)] = { 0 };
 
@@ -806,6 +805,7 @@ SDL_EVDEV_device_added(const char *dev_path, int udev_class)
     if (udev_class & (SDL_UDEV_DEVICE_TOUCHSCREEN | SDL_UDEV_DEVICE_TOUCHPAD)) {
         item->is_touchscreen = SDL_TRUE;
 
+        int ret;
         if ((ret = SDL_EVDEV_init_touchscreen(item, udev_class)) < 0) {
             close(item->fd);
             SDL_free(item->path);

src/core/linux/SDL_evdev_kbd.c

@@ -254,7 +254,7 @@ static void kbd_cleanup_signal_action(int signum, siginfo_t* info, void* ucontex
 
 static void kbd_unregister_emerg_cleanup()
 {
-    int tabidx, signum;
+    int tabidx;
 
     kbd_cleanup_state = NULL;
 
@@ -264,6 +264,7 @@ static void kbd_unregister_emerg_cleanup()
     kbd_cleanup_sigactions_installed = 0;
 
     for (tabidx = 0; tabidx < sizeof(fatal_signals) / sizeof(fatal_signals[0]); ++tabidx) {
+        int signum;
         struct sigaction* old_action_p;
         struct sigaction cur_action;
         signum = fatal_signals[tabidx];
@@ -294,7 +295,7 @@ static void kbd_cleanup_atexit(void)
 
 static void kbd_register_emerg_cleanup(SDL_EVDEV_keyboard_state * kbd)
 {
-    int tabidx, signum;
+    int tabidx;
 
     if (kbd_cleanup_state != NULL) {
         return;
@@ -316,6 +317,7 @@ static void kbd_register_emerg_cleanup(SDL_EVDEV_keyboard_state * kbd)
     kbd_cleanup_sigactions_installed = 1;
 
     for (tabidx = 0; tabidx < sizeof(fatal_signals) / sizeof(fatal_signals[0]); ++tabidx) {
+        int signum;
         struct sigaction* old_action_p;
         struct sigaction new_action;
         signum = fatal_signals[tabidx];   

src/core/linux/SDL_threadprio.c

@@ -302,6 +302,8 @@ SDL_LinuxSetThreadPriorityAndPolicy(Sint64 threadID, int sdlPriority, int schedP
 #if SDL_THREADS_DISABLED
     return SDL_Unsupported();
 #else
+
+#if SDL_USE_LIBDBUS
     int osPriority;
 
     if (schedPolicy == SCHED_RR || schedPolicy == SCHED_FIFO) {
@@ -330,7 +332,6 @@ SDL_LinuxSetThreadPriorityAndPolicy(Sint64 threadID, int sdlPriority, int schedP
         }
     }
 
-#if SDL_USE_LIBDBUS
     /* Note that this fails you most likely:
      * Have your process's scheduler incorrectly configured.
        See the requirements at:

src/core/linux/SDL_udev.c

@@ -162,8 +162,6 @@ SDL_UDEV_Init(void)
 void
 SDL_UDEV_Quit(void)
 {
-    SDL_UDEV_CallbackList *item;
-
     if (_this == NULL) {
         return;
     }
@@ -183,6 +181,7 @@ SDL_UDEV_Quit(void)
 
         /* Remove existing devices */
         while (_this->first != NULL) {
+            SDL_UDEV_CallbackList *item;
             item = _this->first;
             _this->first = _this->first->next;
             SDL_free(item);

src/core/openbsd/SDL_wscons_mouse.c

@@ -57,15 +57,16 @@ SDL_WSCONS_mouse_input_data* SDL_WSCONS_Init_Mouse()
 void updateMouse(SDL_WSCONS_mouse_input_data* inputData)
 {
     struct wscons_event events[64];
-    int type;
-    int n,i;
+    int n;
     SDL_Mouse* mouse = SDL_GetMouse();
 
     if ((n = read(inputData->fd, events, sizeof(events))) > 0)
     {
+        int i;
         n /= sizeof(struct wscons_event);
         for (i = 0; i < n; i++)
         {
+            int type;
             type = events[i].type;
             switch(type)
             {

src/core/os2/geniconv/os2iconv.c

@@ -72,13 +72,13 @@ typedef struct iuconv_obj {
 static int _createUconvObj(const char *code, UconvObject *uobj)
 {
     UniChar uc_code[MAX_CP_NAME_LEN];
-    int i;
     const unsigned char *ch =
          (const unsigned char *)code;
 
     if (code == NULL)
         uc_code[0] = 0;
     else {
+        int i;
         for (i = 0; i < MAX_CP_NAME_LEN; i++) {
             uc_code[i] = (unsigned short)*ch;
             if (! (*ch))

src/core/os2/geniconv/sys2utf8.c

@@ -32,7 +32,6 @@
 
 int StrUTF8(int to_utf8, char *dst, int c_dst, char *src, int c_src)
 {
-    size_t  rc;
     char   *dststart = dst;
     iconv_t cd;
     char   *tocp, *fromcp;
@@ -56,6 +55,7 @@ int StrUTF8(int to_utf8, char *dst, int c_dst, char *src, int c_src)
     }
 
     while (c_src > 0) {
+        size_t rc;
         rc = iconv(cd, &src, (size_t *)&c_src, &dst, (size_t *)&c_dst);
         if (rc == (size_t)-1) {
             if (errno == EILSEQ) {