Remove test for sdl13-config... it's never going to happen.

Test for sdl12-config before sdl-config for systems that have SDL 2.0
installed as sdl-config.

src/xpdev/Common.gmake

@@ -98,22 +98,17 @@ ifdef USE_SDL_AUDIO
     WITH_SDL_AUDIO	:=	1
    endif
   else
-   ifeq ($(shell sdl-config --cflags > /dev/null 2>&1 && echo YES),YES)
-    SDL_CONFIG := sdl-config
+   ifeq ($(shell sdl12-config --cflags > /dev/null 2>&1 && echo YES),YES)
+    SDL_CONFIG := sdl12-config
     WITH_SDL_AUDIO	:=	1
    else
-    ifeq ($(shell sdl13-config --cflags > /dev/null 2>&1 && echo YES),YES)
-     SDL_CONFIG := sdl13-config
+    ifeq ($(shell sdl-config --cflags > /dev/null 2>&1 && echo YES),YES)
+     SDL_CONFIG := sdl-config
      WITH_SDL_AUDIO	:=	1
     else
-     ifeq ($(shell sdl12-config --cflags > /dev/null 2>&1 && echo YES),YES)
-      SDL_CONFIG := sdl12-config
+     ifeq ($(shell sdl11-config --cflags > /dev/null 2>&1 && echo YES),YES)
+      SDL_CONFIG := sdl11-config
       WITH_SDL_AUDIO	:=	1
-     else
-      ifeq ($(shell sdl11-config --cflags > /dev/null 2>&1 && echo YES),YES)
-       SDL_CONFIG := sdl11-config
-       WITH_SDL_AUDIO	:=	1
-      endif
      endif
     endif
    endif