Upgrade JGit to 0.4.0-236-gcb63365

This resolves some issues related to the network protocols for Git.

A deadlock between "git fetch" on the client and a Gerrit SSH server
has been fixed.  This showed up on the Linux kernel repository when
a native Git client was trying to update itself off a Gerrit server.

A bug fix for the number of objects being sent over the wire has
been fixed.  JGit was sending too many objects when there was a
known common base between two peers.  This resulted in too many
objects being sent when updating a replica, or too many objects
being sent during a client fetch request.

A bug fix preventing some changes from being created in Gerrit due
to a failure to compute the revision graph correctly was also fixed.
This was discussed on repo-discuss under [1] but never opened in
the issue tracker.

[1] http://groups.google.com/group/repo-discuss/browse_thread/thread/751481b71556632c

Signed-off-by: Shawn O. Pearce <sop@google.com>
diff --git a/pom.xml b/pom.xml
index df5df46..0176453 100644
--- a/pom.xml
+++ b/pom.xml
@@ -511,7 +511,7 @@
     <dependency>
       <groupId>org.spearce</groupId>
       <artifactId>jgit</artifactId>
-      <version>0.4.0-212-g9057f1b</version>
+      <version>0.4.0-236-gcb63365</version>
       <scope>compile</scope>
     </dependency>