* src/raster/ftraster.c (Insert_Y_Turn): Fix overflow test.

* include/freetype/config/ftoption.h [FT_CONFIG_OPTION_MAC_FONTS]:
New macro.
* src/base/ftobjs.c: Use it to control mac font support on non-mac
platforms.

Implement partial support of Mac fonts on non-Mac platforms.

* src/base/ftobjs.c (memory_stream_close, new_memory_stream,
open_face_from_buffer, Mac_Read_POST_Resource,
Mac_Read_sfnt_Resource, IsMacResource, IsMacBinary, load_mac_face)
[!FT_MACINTOSH]: New functions.
(FT_Open_Face) [!FT_MACINTOSH]: Use load_mac_face.

* src/base/ftobjs.c (FT_Load_Glyph): Scale linear advance width only
if FT_FACE_FLAG_SCALABLE is set (otherwise we have a division by
zero since FNT and friends don't define `face->units_per_EM').