[truetype] Avoid reexecution of `fpgm' and `prep' in case of error.

Reported as


* include/freetype/fterrdef.h (FT_Err_DEF_In_Glyf_Bytecode): New
error code.

* src/truetype/ttinterp.c (Ins_FDEF, Ins_IDEF): Prohibit execution
of these two opcodes in `glyf' bytecode.
(TT_RunIns): Don't enforce reexecution of `fpgm' and `prep' bytecode
in case of error since function tables can no longer be modified
(due to the changes in `Ins_FDEF' and `Ins_IDEF').  This change can
enormously speed up handling of broken fonts.
3 files changed