status/words: shorten list of revisions on buildStarted

Even when useRevisions was false, the IRC bot would under some circumstances
flood the IRC channel by sending long lists of revisions. This changes shortens
the list to only two revisions, and the number of additional revisions included
in the build.
Add createAbsoluteSourceStamps argument to Nightly

This is based on pull request #758.

When multiple codebases are used and createAbsoluteSourceStamps is
enabled, it uses the last revision seen for each codebase without
changes when creating the buildset. This stops any changes from the time
the buildset it created and source step is run from being included in
the build.
Run test_error_without_dateutil in own interpreter
Added multiprocessing to Python 2.5 travis config
Merge branch 'topic/words_dont_userevisions' of git://github.com/olof/buildbot
Merge branch 'nightly-abs-source-stamps' of git://github.com/pepsiman/buildbot
Merge branch 'fix_test_error_without_dateutil' of git://github.com/mihaimartalogu/buildbot
when submitter or owner have no name value will cause exception,fix this by give default value
Add createAbsoluteSourceStamps back to doc for SingleBranchScheduler
Don't refer to following fields when there aren't any
Merge branch 'gerritfix' of git://github.com/zhangchunlin/buildbot
Merge branch 'nightly-abs-source-stamps' of git://github.com/pepsiman/buildbot
Merge branch 'following_fields' of git://github.com/pepsiman/buildbot
Don't specify a revision to pull from a mercurial repository

Buildbot trac ticket 438.  Pulling a tag does not guarantee
that mercurial can update to that tag.
Merge branch 'mercurial_tag' of git://github.com/pepsiman/buildbot
Make scheduler reasons consistent
Merge branch 'reason' of git://github.com/pepsiman/buildbot
Fix reason for Triggerable scheduler.  Add reason tests
Merge branch 'reason' of git://github.com/pepsiman/buildbot
set .master for buildsteps