Rename the _MD macro to D_METHOD

This new name also makes its purpose a little clearer

This is a step towards fixing #56

platform/android/java_class_wrapper.cpp

@@ -562,7 +562,7 @@ JavaObject::~JavaObject(){
 
 void JavaClassWrapper::_bind_methods() {
 
-	ClassDB::bind_method(_MD("wrap:JavaClass","name"),&JavaClassWrapper::wrap);
+	ClassDB::bind_method(D_METHOD("wrap:JavaClass","name"),&JavaClassWrapper::wrap);
 }