Non-standard: add Microsoft ES3 extensions

[webbedspace]

All the non-DOM-related extensions are here. Mostly I'm interested in:

• CollectGarbage()
• RuntimeObject() (searches the window object for properties created by var statements or implicit globals, whose names match the search string)
• RegExpError
• RegExp constructor static properties: RegExp.index, RegExp.input, RegExp.lastIndex, RegExp.lastMatch, RegExp.lastParen, RegExp.leftContext, RegExp.rightContext, RegExp.$_, RegExp["$&"], RegExp["$+"], RegExp["$"], RegExp["$'"]`
• RegExp "options" property (equals the string "igm" for /./gim, etc.)

I'm leaving off everything that interacts with ActiveXObject, though, as well as the fairly useless ScriptEngine functions that just return version strings.

[kangax]

Good stuff!

[chicoxyzzy]

Do we still want this?

[ljharb]

We want everything that’s in engines; especially the regexp globals.