Introduces GWT.reportUncaughtException.

This patch adds GWT.reportUncaughtException as a replacement of the
earlier introduced GWT.maybeReportUncaughtException.

Unlike the previous version, as the name suggests, new one guarantees
that the exception is not swallowed and reported back to the browser
even there is no uncaught exception handler.

Bug: issue 6833
Change-Id: Ica7e86f73807f637535c7fd73b8256189385f9e7
Review-Link: https://gwt-review.googlesource.com/#/c/5416/
Adds event dispatch extension methods to DOMImplStandard

Fixes issue 8379

Change-Id: I7df2678ab26e703b3db437c81ccc8d768b44917e
Fix -saveSourceOutput when target is a directory

The problem is actually that the one-arg version of
OutputFileSet.openForWrite() didn't work, but it is unused
except by SourceSaver.

Wrote javadoc explaining how these methods actually work.

(The OutputFileSet classes are quite messy, but it looks like
this code is intended to avoid touching files unnecessarily
to work well with a Makefile-style build where timestamps
are used to determine whether downstream build rules need
to run. It seems fragile, but I'm ignoring that issue and
just getting -saveSourceOutput to work.)

Change-Id: Iebbad400942115c0acb34fefb1fba502ba8256d8
Remove "-runStyle HtmlUnit:FF3.6" for coverage tests

Support for HtmlUnit's support for FF3.6 was removed when we upgraded
to a newer version of HtmlUnit, and -runStyle HtmlUnit:FF17 is the
default behavior anyway when a run style is not explicitly specified.

Change-Id: Ic2af8dbe040f13c01c21e06606de283535a1581d
Merge remote-tracking branch 'upstream/master'