Support architectures where `long` is smaller than pointers.

I am currently trying to compile FreeType for CHERI-extended ISAs
(CHERI-RISC-V and Arm's Morello), but I am getting compiler warnings
from the `FT_UINT_TO_POINTER` macro.  When compiling with the CHERI
Clang compiler, not using `uinptr_t` for casts between integers an
pointers results in the following `-Werror` build failures:

In file included from .../src/truetype/truetype.c:22:
  .../src/truetype/ttgload.c:1925:22: error:
    cast from provenance-free integer type to pointer type will
    give pointer that can not be dereferenced
  node->data = FT_UINT_TO_POINTER( glyph_index );
  .../include/freetype/internal/compiler-macros.h:79:34: note:
    expanded from macro 'FT_UINT_TO_POINTER'

* include/freetype/internal/compiler-macros.h (FT_UINT_TO_POINTER):
The ISO C standard compliant fix for this would be to use
`uintptr_t` from `stdint.h`, but I am not sure if this is supported
by the minimum compiler version.  Therefore, use the
compiler-defined `__UINTPTR_TYPE__` macro (supported in GCC 4.6+ and
Clang since about 3.0) before checking for `_WIN64` and falling back
to `unsigned long`.
2 files changed