`gd_webp.c` needs `ssize_t` which is defined in `gd_intern.h` for MSVC.

Fixes following errors:
error: a function definition without a prototype is deprecated in all versions of C and is not supported in C2x [-Werror,-Wdeprecated-non-prototype]

Signed-off-by: Khem Raj <raj.khem@gmail.com>

Fix #790, don't rotate glyph positions with Raqm 0.9.0+

Raqm will apply the transformation matrix set on the FT_Face itself.

First, we must not forget to call `avifImageDestroy()` when we're
finished with the image.

Then we also need to cater to the allocated `dataBuf`.  To keep track
of that, we "extend" `avifIO` as `avifIOCtxReader`.  To simplify, and
to avoid unnecessary allocations, we use `realloc()`.  To better fit
with GD, we also use the GD memory allocation functions instead of the
ones provided by libavif.

* Enable webpng on MINGW

* Detect GD version using cmake language

* Use _aligned_malloc instead of posix_memalign on Windows

* Include missing "errno.h"

* Fix finding WEBP on MINGW

* Fix finding XPM on MINGW

* Use PkgConfig to find packages on MINGW

* CI: Enable more options  for MINGW

* Partial #818, unused arg

* Partial #818, init var

* partail #818, fix va_args usage

* partail #818, handle f* calls and avoid possible call to malloc with negative values

* partail #818, prevent double free

* partail #818, resource leak if test fail

* partail #818, null deref fix

* partail #818, avoid double free on fp failure

* Partial #818, fix error msg

* Partial #818, leak on error

* Partial #818, null deref

* Partial #818, avoid possible negative index on failure

* partial #818, does not free if we return if requested new size overflow

* partial #818, avoid double free, free where the alloc happened