Bug 798642. AST 'toSource' on getter/setter mistakenly adding 'function' keyword
https://bugzilla.mozilla.org/show_bug.cgi?id=798642
Bug 800616. Fix AST 'toSource' for Octal and Hexadecimal literals
https://bugzilla.mozilla.org/show_bug.cgi?id=800616
'undefined' pattern should be treated as empty string in RegExp constructor
http://www.ecma-international.org/ecma-262/5.1/#sec-15.10.4.1
https://sourceforge.net/p/htmlunit/bugs/1599/
Merge branch 'Bug-RegExpConstructorUndefined'