Generalizes File... to PersistenceBackedObject

Replaces the last uses of FileBackedObject, with the more
general PersistenceBackedObject so that those pathways
will now be ZipEntryBackedObject compatible.

ZipEntryBackedObject usage needs to work to enable passing
around things pulled out of ZipLibrary instances during
separate compilation.

Separate compilation is something we want because it is
faster.

Change-Id: I6fc3db141ac320228e590264b508fb664807fc03
Fixed, couldn't get SuperSource from libraries.

CompilationUnit lookups were only checking the non-SuperSource
index unit presence and so was incorrectly returning a null for
SuperSource compilation units.

This was causing separate compilation to fail when unable to
resolve references to classes that were only available as
super source. Fixed.

Also clarifies the regular/super source compilation unit
distinction in some getter function names and fixes a bug in
LibraryGroup.getCompilationUnitTypeNames() that became clear
as a result.

Change-Id: I1e8f0124d247c477285faadefdc814f5a826c5cf
Review-Link: https://gwt-review.googlesource.com/#/c/5415/
Allow multiple DomEvent types per DOM event

It’s possible that different libraries provide DomEvent types for the
same DOM event (mainly HTML 5 events, e.g. transitionend). If that
happens only one library will work, as GWT only knows the last
registered DomEvent type. To fix this a one-to-many mapping between
DOM event name and DomEvent types has been introduced.

This patch also contributes to issue 8379 which aims to make the
event system more extendable.

Bug: issue 7698
Change-Id: Iedbac84881484849548e1829d61eb13a6c7d00e3
Add -helpfull and -?? to command-line tools

Change-Id: I18f91d3b58b21395f8bde970edabd4d9edb238cb
Add -saveSourceOutput to the Compiler

Change-Id: I403e1cfdd54dc5fd00fe0172b92a6294f1148f3f
Remove references to JFreeChart.

We don't seem to use it anymore.  Maybe it was part of the benchmarks
framework we deleted a while back?

Change-Id: I9bd406750c167c6fff3130ec6e55ff43df0dd56d
Including GWT's rebased dependencies inside gwt-servlet.jar

Changed Ant's build.xml for gwt-servlet.jar so to include a selection of
libraries rebased for specific use in GWT and that may be required
also on server side:
- sourcemaps is used by StackTraceDeobfuscator,
- streamhtmlparser is required for SafeHtml
- guava is needed by both.
- protobuf needed for sourcemaps and devmode.
(see also linked issue).

Bug: issue 8438
Change-Id: I73df9d03368785a3625c3a48ee989dc919738e83
Merge remote-tracking branch 'upstream/master'