This isn't C++ code, so there's no need to append global symbols with two
colons. It looks ugly.
I _did_ leave them for actual C++ things in WinRT-specific comments and other
places, like a reference to a Perl class thing.
Also, even though it's not valid C, it's a useful expression to say
`StructType::SpecificField`, so I left those alone, too.
This takes care of the last set of void functions that could
potentially be shifted to instead return an int indicating success and
setting an error in case of an error.
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