Avoid compiler warnings related to mbstring flush functions

Author: alexdowad

ext/mbstring/libmbfl/filters/mbfilter_cp5022x.c

@@ -585,7 +585,7 @@ mbfl_filt_conv_wchar_cp50220_ctor(mbfl_convert_filter *filt)
 	ctx->last.opaque = ctx;
 	ctx->last.data = filt->data;
 	filt->filter_function = vtbl_tl_jisx0201_jisx0208.filter_function;
-	filt->filter_flush = vtbl_tl_jisx0201_jisx0208.filter_flush;
+	filt->filter_flush = (filter_flush_t)vtbl_tl_jisx0201_jisx0208.filter_flush;
 	filt->output_function = (output_function_t)ctx->last.filter_function;
 	filt->flush_function = (flush_function_t)ctx->last.filter_flush;
 	filt->data = &ctx->last;

ext/mbstring/libmbfl/mbfl/mbfl_convert.c

@@ -136,7 +136,7 @@ static void mbfl_convert_filter_common_init(mbfl_convert_filter *filter, const m
 	filter->filter_ctor = vtbl->filter_ctor;
 	filter->filter_dtor = vtbl->filter_dtor;
 	filter->filter_function = vtbl->filter_function;
-	filter->filter_flush = vtbl->filter_flush;
+	filter->filter_flush = (filter_flush_t)vtbl->filter_flush;
 	filter->filter_copy = vtbl->filter_copy;
 
 	(*filter->filter_ctor)(filter);