Move the _warn_if_deprecated call from repo.__init__ to
repo.lock_{read,write} so that branch.lock_{read,write} can call it. This
makes it possible to access locations.conf and branch.conf.

* bzrlib/tests/blackbox/test_exceptions.py:
(TestDeprecationWarning): Test that the suppress_warning
configuration variable is taken into account.

* bzrlib/repository.py:
(Repository.__init__): Delete very old and obsolete
comments. Don't warn about deprecations yet.
(Repository.lock_write, Repository.lock_read): The repo is about
to be locked, check deprecation.
(Repository._warn_if_deprecated): Use the branch config if
available or the global one othewrwise and check for the
suppress_warning variable.

* bzrlib/remote.py:
(RemoteRepository._warn_if_deprecated): Nothing to do here. 

* bzrlib/repofmt/pack_repo.py:
(KnitPackRepository._warn_if_deprecated): Delegate to base class
if needed.

* bzrlib/branch.py:
(BzrBranch.lock_write, BzrBranch.lock_read): Check repo
deprecation.

* bzrlib/help_topics/en/configuration.txt:
Fix the variable name and its description.