[Savannah bug #43682] Change some signatures to `void' return type.
* include/internal/pshints.h (PSH_Globals_SetScaleFunc),
include/internal/sfnt.h (TT_Get_Metrics_Func),
src/pshinter/pshglob.c (psh_globals_set_scale),
src/pshinter/pshrec.c (ps_hints_init), src/sfnt/ttmtx.c
(tt_face_get_metrics), src/truetype/ttinterp.c (TT_Goto_CodeRange,
TT_Set_CodeRange, TT_Clear_CodeRange, TT_Done_Context,
TT_Save_Context): Do it.
* src/pshinter/pshglob.h, src/pshinter/pshrec.h, src/sfnt/ttmtx.h,
src/truetype/ttgload.c (TT_Hint_Glyph), src/truetype/ttinterp.c
(TT_Run_Context), src/truetype/ttinterp.h, src/truetype/ttobjs.c
(tt_size_run_fpgm, tt_size_run_prep): Updated.
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