10l typo: libdir --> incdir

git-svn-id: file:///var/local/repositories/ffmpeg/trunk@4988 9553f0bf-9b14-0410-a0b8-cfaf0461ba5b

configure

@@ -1306,7 +1306,7 @@ libdir="${prefix}/lib"
 fi
 
 if test x"$incdir" = x""; then
-libdir="${prefix}/include/ffmpeg"
+incdir="${prefix}/include/ffmpeg"
 fi
 
 if test x"$mandir" = x""; then