Synch with ffmpeg's r6938 "allow spaces in source and build directory names..."

git-svn-id: file:///var/local/repositories/mplayer/trunk/libswscale@20816 b3059339-0415-0410-9bf9-f77b7e298cf2

Makefile

@@ -16,7 +16,7 @@ endif
 
 HEADERS = swscale.h rgb2rgb.h
 
-include $(SRC_PATH)/common.mak
+include ../common.mak
 
 cs_test: cs_test.c $(LIB)