change __stdcall to FFMS_CC, should improve portability

Originally committed to SVN as r2397.

aegisub/ffmpegsource_common.cpp

@@ -41,7 +41,7 @@
 
 ///////////////
 // Update indexing progress
-int __stdcall FFmpegSourceProvider::UpdateIndexingProgress(int State, int64_t Current, int64_t Total, void *Private) {
+int FFMS_CC FFmpegSourceProvider::UpdateIndexingProgress(int State, int64_t Current, int64_t Total, void *Private) {
 	IndexingProgressDialog *Progress = (IndexingProgressDialog *)Private;
 
 	if (Progress->IndexingCanceled)

aegisub/ffmpegsource_common.h

@@ -53,7 +53,7 @@ public:
 		DialogProgress *ProgressDialog;
 	};
 
-	static int __stdcall UpdateIndexingProgress(int State, int64_t Current, int64_t Total, void *Private);
+	static int FFMS_CC UpdateIndexingProgress(int State, int64_t Current, int64_t Total, void *Private);
 	FrameIndex *DoIndexing(FrameIndex *Index, wxString Filename, wxString Cachename, int Trackmask, bool IgnoreDecodeErrors);
 };