Added Source:clone() and love.audio.newSource(source): creates a new (stopped) Source which has all of the settable state of the original.

Static sources don’t duplicate their OpenAL data buffer when cloned (resolves issue #319). Cloned streaming sources also clone the original Decoder.

src/modules/audio/null/Source.cpp

@@ -36,7 +36,7 @@ Source::~Source()
 {
 }
 
-love::audio::Source *Source::copy()
+love::audio::Source *Source::clone()
 {
 	this->retain();
 	return this;