Fix regex.c test function printouts.
Implement Function.prototype.bind().
Use array helper functions.
Handle NaN and Infinity in Number.toFixed and friends.
Add user customisable panic function.

Intended to let the user longjmp to their own error recovery, if an
error occurs in an unprotected call.

Protected calls so far are only js_newstate, js_dofile and js_dostring.
Add protected functions to load and call code.

So that clients don't need to know about js_try.
Some tidying.
Add and use js_touint16.