Add patcheck checks for assignments that look like compound assignments

Patch by Eli Friedman, eli dot friedman at gmail

Originally committed as revision 23841 to svn://svn.ffmpeg.org/ffmpeg/trunk

tools/patcheck

@@ -42,6 +42,7 @@ hiegrep '/\*[-<\* ]*\*/'  'empty comment' $*
 hiegrep 'for *\( *'"$ERE_PRITYP"' '  'not gcc 2.95 compatible' $*
 hiegrep '(static|inline|const) *\1'  'duplicate word' $*
 hiegrep 'INIT_VLC_USE_STATIC' 'forbidden ancient vlc type' $*
+hiegrep '=[-+\*\&] ' 'looks like compound assignment' $*
 
 hiegrep2 '(int|unsigned|static|void)[a-zA-Z0-9 _]*(init|end)[a-zA-Z0-9 _]*\(.*[^;]$' '(av_cold|:\+[^a-zA-Z_])' 'These functions may need av_cold, please review the whole patch for similar functions needing av_cold' $*