I ran this script in the include directory:
```sh
sed -i '' -e 's,#include "\(SDL.*\)",#include <SDL3/\1>,' *.h
```
I ran this script in the src directory:
```sh
for i in ../include/SDL3/SDL*.h
do hdr=$(basename $i)
if [ x"$(echo $hdr | egrep 'SDL_main|SDL_name|SDL_test|SDL_syswm|SDL_opengl|SDL_egl|SDL_vulkan')" != x ]; then
find . -type f -exec sed -i '' -e 's,#include "\('$hdr'\)",#include <SDL3/\1>,' {} \;
else
find . -type f -exec sed -i '' -e '/#include "'$hdr'"/d' {} \;
fi
done
```
Fixes https://github.com/libsdl-org/SDL/issues/6575
As well as reducing duplication, this lets the tests load their resources
from the SDL_GetBasePath() on platforms that support it, which is useful
if the tests are compiled along with the rest of SDL and installed below
/usr as manual tests, similar to GNOME's installed-tests convention.
Thanks to Ozkan Sezer for the OS/2 build glue.
Co-authored-by: Ozkan Sezer <sezeroz@gmail.com>
Signed-off-by: Simon McVittie <smcv@collabora.com>
