add .lastIndex to RegExp
Merge branch 'master' of github.com:micnic/runtime
fix .lastIndex reset after multiple RegExp.exec() calls + added tests for regex
Merge #501 r=@tcr: Added .lastIndex to RegExp

Related to the issues #491 and #494 (duplicate of #491)

Added .lastIndex to the `RegExp` objects and fixed `RegExp.prototype.exec` with global flag and multiple calls