Prefix some calls with std::

These depend on C++ argument dependent name lookup and won't work with
an upcoming cleanup.

src/SongManager.cpp

@@ -2124,7 +2124,7 @@ void SongManager::AddSongToList(Song* new_song)
 	m_pSongs.push_back(new_song);
 	RString dir= new_song->GetSongDir();
 	dir.MakeLower();
-	m_SongsByDir.insert(make_pair(dir, new_song));
+	m_SongsByDir.insert(std::make_pair(dir, new_song));
 }
 
 void SongManager::FreeAllLoadedFromProfile( ProfileSlot slot )