tune widget system performance

[alex]

the widget system in 0.9 is pretty quick, but we should keep an eye on the ball. This is a general bug for widget tuning purposes. Checkins logged here should note the performance differences that go along w/ each change.

[alex]

(In [8685]) updates to improve the performance of _createNodesFromText. This checkins:

• replaces the cloning logic w/ direct node removal
• reuses the encapsulating node
• moves regular expression calculations out of the fast path and moves string trimming to the caching logic (verified that it's not called outside of this code path)
• hoists at least one invariant out of a loop (and this is regexp replacement, so it matters)
• moves "appendChild" logic for putting nodes in the rendered DOM to after the replacement of the innerHTML of the container

On the "themeTest.html" page, these changes reduced the time to construct the ~90 widgets on that page by nearly 20ms (112ms->93ms, avg).

Refs #3092

[alex]

(In [8686]) move the regexes out of the fast path so that there's less chance they'll be recompiled. Drops heavy dojo._Url usage speed by ~20%. Refs #3092

[alex]

(In [8688]) profiling page cleanup to enable better testing. Refs #3092

[Adam Peller]

(In [9866]) Move source uri hint to end of file (for firebug 1.1) so that it won't throw off the line count in the eval buffer by 1. Refs #3092