Properly export all lua-facing functions and use those for initialization (love.cpp no longer explicitly mentions implementations)

src/modules/graphics/opengl/wrap_Font.h

@@ -37,7 +37,7 @@ namespace opengl
 	int w_Font_getWrap(lua_State * L);
 	int w_Font_setLineHeight(lua_State * L);
 	int w_Font_getLineHeight(lua_State * L);
-	int luaopen_font(lua_State * L);
+	extern "C" int luaopen_font(lua_State * L);
 
 } // opengl
 } // graphics