Fix for previous commit, which caused many compiler warnings/errors
about addresses of volatile objects passed as function arguments
as non-volatile pointers.
* freetype2/include/freetype/internal/ftvalid.h: Make
FT_Validator typedef a pointer to a volatile object.
* freetype2/src/gxvalid/gxvmod.c (gxv_load_table): Make function
argument `table' a pointer to a volatile object.
* freetype2/src/otvalid/otvmod.c (otv_load_table): Make function
argument `table' a pointer to a volatile object.
* freetype2/src/gxvalid/gxvmod.c (GXV_TABLE_DECL): Mark local
variable `_sfnt' as volatile since it must keep its value across
a call to ft_setjmp.
(gxv_validate): Same for local variables `memory' and `valid'.
(classic_kern_validate): Same for local variables `memory',
`ckern', and `valid'.
* freetype2/src/otvalid/otvmod.c (otv_validate): Same for function
parameter `face' and local variables `base', `gdef', `gpos', `gsub',
`jstf', and 'valid'.
* freetype2/src/sfnt/ttcmap.c (tt_face_build_cmaps): Same for
local variable `cmap'.
