Fix ses.funcLike protection against non-identifier names.

Any non-identifier or possible non-identifier will now be correctly
rejected. Additionally, if the name merely contains a space (as in
(function f() {}).bind().name === "bound f"), replace it with an
underscore to make it valid.

Fixes https://github.com/google/caja/issues/2001.

@ 9f33b649ae8c2e8c068e1f03753ee275ccc0981d

[MarkM, 2016-05-27 23:01:50]

LGTM