Rename macros with two leading underscores

These names are reserved for the compiler/library implementations.

src/content_sao.cpp

@@ -393,7 +393,7 @@ std::string LuaEntitySAO::getClientInitializationData(u16 protocol_version)
 
 std::string LuaEntitySAO::getStaticData()
 {
-	verbosestream<<__FUNCTION_NAME<<std::endl;
+	verbosestream<<FUNCTION_NAME<<std::endl;
 	std::ostringstream os(std::ios::binary);
 	// version
 	writeU8(os, 1);