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-simple-atom-and-iterations.js

@@ -88,3 +88,6 @@ assert (r.exec ("\\c3") == "\\c3");
 
 r = /\cIasd/;
 assert (r.exec ("\tasd") == "\tasd");
+
+r = /.??$/;
+assert (JSON.stringify (r.exec("asd")) === '["d"]');