added option to disable sdl mixer support

configure.in

@@ -68,26 +68,30 @@ 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
-if test x"$sdlmixer_prefix" != "x"; then
+     AC_MSG_WARN(Disable SDLMixer support)
+	 have_sdl_mixer=no
+else
+	if test x"$sdlmixer_prefix" != "x"; then
   		SDLMIXER_LIB="-L$sdlmixer_prefix/lib"
   		SDLMIXER_CFLAGS="-I$sdlmixer_prefix/include"
   		LDFLAGS="$SDLMIXER_LIB $LDFLAGS"
   		CFLAGS="$CFLAGS $SDLMIXER_CFLAGS"
-fi
+	fi
 
-AC_CHECK_LIB(SDL_mixer, Mix_OpenAudio, have_sdl_mixer="yes", have_sdl_mixer="no" , )
+	AC_CHECK_LIB(SDL_mixer, Mix_OpenAudio, have_sdl_mixer="yes", have_sdl_mixer="no" , )
 
-if test "x$have_sdl_mixer" = "xyes"; then
+	if test "x$have_sdl_mixer" = "xyes"; then
  		AC_DEFINE(HAVE_SDL_MIXER, [1], [SDL_mixer])
  		LIBS="$LIBS -lSDL_mixer"
-else
+	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.
 dnl Check for rintf and functions like that
 AC_MSG_CHECKING(for rintf)