Add (mostly) const to variable and parameter declaration, where a char* was

used and 'const char*' should be, plus make some function declarations
static if they aren't used outside their declaring source file.
patch by Stefan Huehner stefan%%at%%huehner%%dot%%org

Originally committed as revision 5492 to svn://svn.ffmpeg.org/ffmpeg/trunk

libavformat/yuv4mpeg.c

@@ -35,7 +35,7 @@ static int yuv4_generate_header(AVFormatContext *s, char* buf)
     int width, height;
     int raten, rated, aspectn, aspectd, n;
     char inter;
-    char *colorspace = "";
+    const char *colorspace = "";
 
     st = s->streams[0];
     width = st->codec->width;