Revert "Merge branch 'jc/graduate-remote-hg-bzr' (early part)"

Instead of showing a warning and working as before, fail and show
the message and force immediate upgrade from their upstream
repositories when these tools are run, per request from their
primary author.

Signed-off-by: Junio C Hamano <gitster@pobox.com>

Documentation/RelNotes/2.0.0.txt

@@ -55,6 +55,9 @@ UI, Workflows & Features
  * The "multi-mail" post-receive hook (in contrib/) has been updated
    to a more recent version from the upstream.
 
+ * The "remote-hg/bzr" remote-helper interfaces (in contrib/) are
+   now maintained separately as a third-party plug-in.
+
  * "git gc --aggressive" learned "--depth" option and
    "gc.aggressiveDepth" configuration variable to allow use of a less
    insane depth than the built-in default value of 250.
@@ -88,6 +91,10 @@ UI, Workflows & Features
  * "git grep" learned to behave in a way similar to native grep when
    "-h" (no header) and "-c" (count) options are given.
 
+ * "git push" via transport-helper interface has been updated to
+   allow forced ref updates in a way similar to the natively
+   supported transports.
+
  * The "simple" mode is the default for "git push".
 
  * "git add -u" and "git add -A", when run without any pathspec, is a