Remove SDL2_image dependency.

chocolate-doom sdl2-branch no longer depends on SDL2_image as of commit
chocolate-doom/chocolate-doom@7215d13b6c, so remove this dependency
and the SDL2_image package.

pkgdef/SDL2_image.sh

@@ -1,19 +0,0 @@
-description "SDL imaging library"
-dependencies SDL2
-check_pkgconfig SDL2_image
-
-variant stable fetch_download \
-    https://www.libsdl.org/projects/SDL_image/release/SDL2_image-2.0.1.tar.gz \
-    3a3eafbceea5125c04be585373bfd8b3a18f259bd7eae3efc4e6d8e60e0d7f64
-variant latest fetch_hg https://hg.libsdl.org/SDL_image/
-
-# SDL2_image supports lots of different file formats but we only care
-# about .png files. So just build a really thin library without support
-# for all the other formats we don't care about.
-# We also disable the OS X ImageIO plugin, and link directly to libpng
-# rather than searching for it at runtime.
-build_autotools --disable-imageio --disable-png-shared \
-    --disable-bmp --disable-gif --disable-jpg --disable-lbm --disable-pcx \
-    --disable-pnm --disable-tga --disable-tif --disable-xcf --disable-xpm \
-    --disable-xv --disable-webp
-

pkgdef/chocolate-doom.sh

@@ -1,5 +1,5 @@
 description "Conservative, historically-accurate Doom source port"
-dependencies SDL2 SDL2_mixer SDL2_net SDL2_image
+dependencies SDL2 SDL2_mixer SDL2_net
 variant latest fetch_git \
     https://github.com/chocolate-doom/chocolate-doom.git sdl2-branch
 build_autotools