lavfi: let gcc realign the stack on public graph driving functions

The functions which actually drive the filter graph by pushing
frames through it need to ensure an aligned stack for SIMD functions.

This fixes a crash in YADIF filter when using a mingw build in a MSVC application.
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

libavfilter/buffersink.c

@@ -117,7 +117,7 @@ int av_buffersink_get_frame(AVFilterContext *ctx, AVFrame *frame)
     return av_buffersink_get_frame_flags(ctx, frame, 0);
 }
 
-int av_buffersink_get_frame_flags(AVFilterContext *ctx, AVFrame *frame, int flags)
+int attribute_align_arg av_buffersink_get_frame_flags(AVFilterContext *ctx, AVFrame *frame, int flags)
 {
     BufferSinkContext *buf = ctx->priv;
     AVFilterLink *inlink = ctx->inputs[0];
@@ -169,7 +169,7 @@ static int read_from_fifo(AVFilterContext *ctx, AVFrame *frame,
 
 }
 
-int av_buffersink_get_samples(AVFilterContext *ctx, AVFrame *frame, int nb_samples)
+int attribute_align_arg av_buffersink_get_samples(AVFilterContext *ctx, AVFrame *frame, int nb_samples)
 {
     BufferSinkContext *s = ctx->priv;
     AVFilterLink   *link = ctx->inputs[0];
@@ -264,7 +264,7 @@ static void compat_free_buffer(AVFilterBuffer *buf)
     av_free(buf);
 }
 
-static int compat_read(AVFilterContext *ctx, AVFilterBufferRef **pbuf, int nb_samples, int flags)
+static int attribute_align_arg compat_read(AVFilterContext *ctx, AVFilterBufferRef **pbuf, int nb_samples, int flags)
 {
     AVFilterBufferRef *buf;
     AVFrame *frame;
@@ -348,7 +348,7 @@ AVRational av_buffersink_get_frame_rate(AVFilterContext *ctx)
     return ctx->inputs[0]->frame_rate;
 }
 
-int av_buffersink_poll_frame(AVFilterContext *ctx)
+int attribute_align_arg av_buffersink_poll_frame(AVFilterContext *ctx)
 {
     BufferSinkContext *buf = ctx->priv;
     AVFilterLink *inlink = ctx->inputs[0];

libavfilter/buffersrc.c

@@ -113,8 +113,8 @@ int av_buffersrc_add_frame_flags(AVFilterContext *ctx, AVFrame *frame, int flags
     return ret;
 }
 
-static int av_buffersrc_add_frame_internal(AVFilterContext *ctx,
-                                           AVFrame *frame, int flags)
+static int attribute_align_arg av_buffersrc_add_frame_internal(AVFilterContext *ctx,
+                                                               AVFrame *frame, int flags)
 {
     BufferSourceContext *s = ctx->priv;
     AVFrame *copy;