Remove references to old LOVE_ENABLE_module_implementation defines

As far as I know they are no longer used, as autotools was the primary (only)
user and it now switches entire modules.
I've also taken the opportunity to clean up the default list in
src/common/config.h.
Oh yeah, and this fixes linux builds not having graphics or audio backends.

--HG--
branch : minor

src/modules/graphics/wrap_Graphics.cpp

@@ -30,9 +30,7 @@
 #include "common/Reference.h"
 #include "math/wrap_Transform.h"
 
-#ifdef LOVE_ENABLE_GRAPHICS_OPENGL
 #include "opengl/Graphics.h"
-#endif
 
 #include <cassert>
 #include <cstring>
@@ -2637,11 +2635,7 @@ extern "C" int luaopen_love_graphics(lua_State *L)
 	Graphics *instance = instance();
 	if (instance == nullptr)
 	{
-#ifdef LOVE_ENABLE_GRAPHICS_OPENGL
 		luax_catchexcept(L, [&](){ instance = new love::graphics::opengl::Graphics(); });
-#else
-		return luaL_error(L, "LOVE was compiled without any love.graphics backend!");
-#endif
 	}
 	else
 		instance->retain();