Rework RegExp engine and add support for proper unicode matching (#3746)

This change includes several bugfixes, general improvements, and support
for additional features.
- Added full support for web compatibility syntax defined in Annex B
- Implemented parsing and matching patterns in unicode mode
- Fixed capture results when iterating with nested capturing groups
- Significantly reduced regexp bytecode size
- Reduced stack usage during regexp execution
- Improved matching performance

JerryScript-DCO-1.0-Signed-off-by: Dániel Bátyai dbatyai@inf.u-szeged.hu

tests/jerry/regexp-capture-groups.js

@@ -196,3 +196,12 @@ assert (r.exec("aa") == "aa,a");
 
 r = new RegExp ("(a{0,1}?){0,1}a");
 assert (r.exec("aa") == "aa,a");
+
+r = new RegExp ("(|.)+");
+assert (JSON.stringify (r.exec("asdfgh")) === '["asdfgh","h"]');
+
+assert (JSON.stringify (/([^\W](){8,}?){5}/.exec("asdfghijk")) === '["asdfg","g",""]');
+assert (JSON.stringify (/(()+?(.+)|){3,}./u.exec("asdfghi")) === '["asdfghi","",null,null]')
+assert (JSON.stringify (/(()+?(.+)|){3,}?./u.exec("asdfghi")) === '["asdfghi","",null,null]')
+assert (JSON.stringify (/(?:()+?(.+)|){3,}./u.exec("asdfghi")) === '["asdfghi",null,null]')
+assert (JSON.stringify (/(?:()+?(.+)|){3,}?./u.exec("asdfghi")) === '["asdfghi",null,null]')