Very annoying exception when using Firebug break on error with dojo

[kludgeless]

See this post for details:

​http://stackoverflow.com/questions/2730084/permissions-error-when-debugging-with-dojo-src

Exceptions should be the exception and not the rule. This exception is fired every time you run dojo in Firefox, unless you're running it in an extension. This branch of code should be skipped based on some other conditional. A djconfig option that extension providers must set, or some other env var that is/could be common to extensions seems like a reasonable approach.

[James Burke]

(In [22130]) Refs #7757 and Fixes #11090, do not throw an error for just running dojo.js from source in firefox with firebug gbreaking on all errors. Start the migration to hostenvs explicitly indicated by the user as it will be increasingly hard to detect the correct hostenv anyway. \!strict