Do not assume the SDL_image and SLD_mixer libraries are installed at the same
prefix reported by sdl-config, but instead get flags from the pkg-config files
installed with these libraries.

--- a/SConscript	2011-12-24 15:46:47.000000000 -0600
+++ b/SConscript	2014-06-12 21:20:45.702668330 -0500
@@ -199,7 +199,13 @@
                 self.fatal_error += "  * library 'png' not found\n"
 
     def configure_sdl(self):
-        if self.conf.CheckMyProgram('sdl-config'):
+        if self.conf.CheckMyProgram('pkg-config'):
+            self.conf.env.ParseConfig("pkg-config --cflags --libs sdl")
+            for sdllib in ['image', 'mixer']:
+                self.conf.env.ParseConfig("pkg-config --cflags --libs SDL_%s" % sdllib)
+                if not self.conf.CheckSDLLib(sdllib):
+                    self.fatal_error += "  * SDL library '%s' not found\n" % sdllib
+        elif self.conf.CheckMyProgram('sdl-config'):
             self.conf.env.ParseConfig("sdl-config  --cflags --libs | sed 's/-I/-isystem/g'")
             for sdllib in ['image', 'mixer']:
                 if not self.conf.CheckSDLLib(sdllib):