Set no-cache headers for nearly all Super Dev Mode pages

This is necessary for IE9 and IE10 (at least).

Change-Id: Ib8ca44580349666079b1c461c55a7c1bd331b8ed

Workaround for webapp classloader regression in DevMode

Allow org.eclipse.jetty classes and friends (Jasper, Xerces) to be
loaded from the classpath without adding the containing JAR
(probably gwt-dev) to the webapp classloader.
Jasper and Xerces were previously added as system classes (from
Jetty's terminology), taking precedence over JARs from WEB-INF/lib;
this change make them "normal" classes with a special classloader
fallback behavior (fallback to the system classloader, without adding
the containing JAR to the webapp classloader).

Also fixes resource loading when trying to load server resources (from
Jetty's terminology) by not allowing them to be loaded from the
classpath.

Bug: issue 8526, issue 8585
(cherry picked from commit abb1c56)
Change-Id: I77611c40bd16ecb39d5c288b8e82647f65f47c86

Fix non determinism in code generation.

GenerateJavaScriptAst.FixNameClashesVisitor fixes name clashes in
a non deterministic order due to iteration over a HashMultimap.

This fix makes the iteration order deterministic by using a
LinkHashMultimap instead.

Change-Id: Iaa878666f4fbae7cf235d3d53f223d8a08af6e4f
(cherry picked from commit d94b402)

Use -war instead of -out for generated project files

Bug: issue 8542
Change-Id: Iad321e52848b9ceba18d200bf39b5b571897d2c6
(cherry picked from commit c894264)

Disable Super Dev Mode in web workers

There are linkers that subclass CrossSiteIFrameLinker but run in
environments where 'window' is undefined. Don't include the
Super Dev Mode hook, since it assumes 'window'.

Change-Id: I5d381fc29ca1738068fa5b8f259dd1ac4ed65221

Restore About.GWT_VERSION_NUM for 2.6.0 release.

Fixes "unknown version" warning from old versions of GPE.

Bug: issue 8430
Change-Id: I9eebc13c2a397c98d38e1327514272a6c5f547e0

Disables Opera permutation

Opera uses webkit permutation with the recent Chromium based
versions and GWT will drop seperate Opera permutation in the
next release after 2.6.

Change-Id: Ifbde48ca3f41239cb3b19137b61c332cbddc334d
(cherry picked from commit 147ed73)

Upgrades HtmlUnit and it dependencies

Some major upgrades:
  /htmlunit
  /jetty
  /apache/commons
  /apache/http
  /xerces
  /tomcat/servlet-api

Fixes issue 7224

Change-Id: I36cc569c2926aa59ee7375e719b917d6d3681a43
Review-Link: https://gwt-review.googlesource.com/#/c/4323/

Tag 2.5.1 release.

git-svn-id: https://google-web-toolkit.googlecode.com/svn/tags/2.5.1@11556 8db76d5a-ed1c-0410-87a9-c151d255dfc7

Tag 2.5.1-RC1

git-svn-id: https://google-web-toolkit.googlecode.com/svn/tags/2.5.1-rc1@11498 8db76d5a-ed1c-0410-87a9-c151d255dfc7