Update Buck

Number of bugs were fixed in recent Buck version:

* java_binary: manifest_file rejects target name as input [1]
* java_binary: optionally suppress manifest merging from dependent
JARs [2]
* java_library(): changing deps to provided_deps doesn't trigger
library rebuild [3]
* genrule: Make deps to $(exe :foo) and $(location :bar) implicitly
[4]

[1] https://github.com/facebook/buck/issues/126
[2] https://github.com/facebook/buck/pull/87
[3] https://github.com/facebook/buck/issues/133
[4] https://github.com/facebook/buck/issues/128

Change-Id: I8fb9f57676eac242b54892a50d90773bfc5cb0c0
Buck: Remove usage of genfile()

genfile() is considered to be deprecated and is going to be discontinued
in future Buck releases [1].

[1] https://groups.google.com/forum/#!topic/buck-build/Ci8Y95USD8I

Change-Id: I7a5a1ee99d1448c412bb51b793c1e874dd3c62f4
Buck: Make deps to $(exe :foo) and $(location :bar) implicitly

Apply [1] on our Buck tree.

[1] https://github.com/facebook/buck/issues/128

Change-Id: Ie3a9de0b2ee3725170bcbd06df059ea5d9ae5252
Buck: Export gwtui-common in gwtui-api-lib

Plugins with GWT modules need both:

* gerrit-plugin-gwtui
* gerrit-gwtui-common

Export gerrit-gwtui-common in gwtui-api-lib so that only one dependency
is needed to link against in tree plugin build.

This is the same behaviour as when the plugin is built against published
plugin API (we don't publish gwtui-common as standalone artifact).

Change-Id: If8da90dc1038b6d4145d2e2bab333c2642e3c25f
Store ChangeMessage in body of commit message

Taught ChangeUpdate how to write out the ChangeMessage into
the message. Also taught ChangeNotes how to parse the
ChangeMessage out of the commit message.

Change-Id: I563eabbd848364150fdf8a5c4af5a2e1562aaefe