initial String.prototype.match support, calling @@match.  do most of the implementation in RegExp.  also, rename String.prototype.contains to String.prototype.includes
more regexp symbol prototype methods.  also add Regexp.prototype.flags getter
add Symbol.split and Symbol.search, along with (unimplemented) regexp methods
moar tests (for RegExp.prototype.flags and +0/-0 in Map/set)
+0/-0 fixes