This changes the type of setters to JSStrictPropertyOp, which is just like
JSPropertyOp except that it takes a 'JSBool strict' argument. Most of the
patch is introducing distinct types and using the appropriate stubs.
The following are left for subsequent patches:
x Similar fixes to the browser outside SpiderMonkey.
x Actually *using* the newly available strictness information. This patch
should have no user-visible effect. I didn't want the interesting stuff
to get lost in this noise.
