* Don't interpret strings with escaped content as directive
* Don't interpret strings after empty statement as directive
* Adapt output to prevent strings being represent as directive
* Introduce UGLIFY_DEBUG to allow internal testing like EXPECT_DIRECTIVE
In uglify-js@1, both parser and tokenizer methods were exported
This allows to use tokenizer() separately, e.g. to wrap or override it, as
parse() method accepts not only text, but also tokenized functions.
