added option to disable sdl mixer support

configure.in

@@ -68,8 +68,12 @@ esac
 
 
 dnl SDL_mixer **********************************
+AC_ARG_ENABLE(sdlmixer, [  --disable-sdlmixer      Do not compile with SDL Mixer support ])
 AC_ARG_WITH(sdlmixer-prefix, [  --with-sdlmixer-prefix=PFX prefix where SDL_mixer library is installed], sdlmixer_prefix="$withval", sdlmixer_prefix="")
-
+if test x$enable_sdlmixer = xno ; then
+     AC_MSG_WARN(Disable SDLMixer support)
+	 have_sdl_mixer=no
+else
 	if test x"$sdlmixer_prefix" != "x"; then
   		SDLMIXER_LIB="-L$sdlmixer_prefix/lib"
   		SDLMIXER_CFLAGS="-I$sdlmixer_prefix/include"
@@ -85,7 +89,7 @@ if test "x$have_sdl_mixer" = "xyes"; then
 	else
  		AC_MSG_WARN([*** libSDL_mixer not found. Make sure you have the development package of SDL_mixer installed - (www.libsdl.org) - or try to use --with-sdlmixer-prefix option])
 	fi
-
+fi
 
 
 dnl Checks for library functions.