contrib: SDL_image: add missing dependencies to .pc file

contrib/src/SDL_image/pkg-config.patch

+--- SDL_image/SDL_image.pc.in.orig	2011-11-15 10:34:23.504770604 -0500
++++ SDL_image/SDL_image.pc.in	2011-11-15 10:34:39.924852030 -0500
+@@ -8,5 +8,6 @@
+ Version: @VERSION@
+ Requires: sdl >= @SDL_VERSION@
+ Libs: -L${libdir} -lSDL_image
++Libs.private:  -ljpeg -ltiff -lpng -lz
+ Cflags: -I${includedir}/SDL
+ 

contrib/src/SDL_image/rules.mak

@@ -16,6 +16,7 @@ $(TARBALLS)/SDL_image-$(SDL_IMAGE_VERSION).tar.gz:
 SDL_image: SDL_image-$(SDL_IMAGE_VERSION).tar.gz .sum-SDL_image
 	$(UNPACK)
 	$(APPLY) $(SRC)/SDL_image/SDL_image.patch
+	$(APPLY) $(SRC)/SDL_image/pkg-config.patch
 	$(MOVE)
 
 DEPS_SDL_image = png $(DEPS_png) jpeg $(DEPS_jpeg) tiff $(DEPS_tiff) \