Refactor emission logic of SAXParser and RewritingStream

[RReverser]

• Fix SAXParser text end location (fixes Incorrect location info in SAXParser and RewritingStream #266).
• Move lazy emission logic from RewritingStream::_handleToken to SAXParser::_handleToken. This allows SAXParser to skip reshaping when no listeners are registered and simplifies interaction between two APIs.
• Make SAXParser::pendingText to keep a CHARACTER token instead of just chars. This aligns emission of pending text with other tokens and gives a single _emitToken point for RewritingStream to override (instead of additionally overriding _emitPendingText with similar logic).
• Remove SAXParser::currentTokenLocation state, instead just retrieving location from current raw or processed token. It was needed mainly to track location for consequent text tokens, but since pendingText is now a token, it can store its own location internally. This additionally allows all reshapeToken helpers to become stateless and live outside of the class.