contrib/Makefile: add SDL as dependency of SDL_image

Signed-off-by: Steven Noonan <steven@uplinklabs.net>

Created by  Steven Noonan  on October 20, 2009
XWWNNQ3GP6JIKEJRBKBRNZETIYDLREGGKEV3UL7W77IY3VPWI67QC
Change contents