Start using intermediate buffers at index 0.

These index variables are incremented before each use, so they should be
initialized to -1.


git-svn-id: file:///var/local/repositories/mplayer/trunk/libswscale@29977 b3059339-0415-0410-9bf9-f77b7e298cf2

swscale_template.c

@@ -2661,8 +2661,8 @@ static int RENAME(swScale)(SwsContext *c, uint8_t* src[], int srcStride[], int s
        will not get executed. This is not really intended but works
        currently, so people might do it. */
     if (srcSliceY ==0) {
-        lumBufIndex=0;
-        chrBufIndex=0;
+        lumBufIndex=-1;
+        chrBufIndex=-1;
         dstY=0;
         lastInLumBuf= -1;
         lastInChrBuf= -1;