[truetype] Honor FT_LOAD_ADVANCE_ONLY if `hdmx` is usable. This simply shortcuts the glyph loading if FT_LOAD_ADVANCE_ONLY is specified by FT_Get_Advances and the `hdmx` data are located. Particularly, the classic v35 interpreter or "verified" ClearType fonts might see 100x speed up in retrieving the hdmx cache. * src/truetype/ttgload.c (TT_Load_Glyph): Insert the shortcut.