Improve parsing of escape characters and regexp literals.

Improve parsing of escape characters and regexp literals.

That is, in QML/JS you can escape characters in identifiers, e.g.

  var c\u0061se = 25

declares a variable called `case' with value 25. In such cases
qmlmin needs to preserve the escape sequence in the declaration.

Also, fix possible errors when pasting keywords after regexp literals.
The minifier needs to preserve the whitespace character after the
regexp delimiter, e.g.

  /x/instanceof blah

without the white space after the regexp, the `i' of `instanceof'
is parsed as a regexp flag.

Change-Id: I5f426ac62949e34d092d4fdb0a41243de8ff2236
Reviewed-by: Kent Hansen <kent.hansen@nokia.com>