improve flattened bundles to provide hints about what wasn't flattened,  refs #17155
account for newline in sourcemap prefix

thanks dellekappa.  fixes #17631
refs #15130. Fixes copyrights date for 2014.
Handle loader plugins used together with dojo/has plugin.  Fixes #17438
refs #17260, fix format of source maps due to spec change
Update the CSS optimizer to end a URL path at a hash as well as a question mark

Fixes #17243
Add new build option useSourceMaps.

True (default) results in source map generation, when supported
by the optimizer. False results in no source maps.

Fixes #17425.