First take on zsh-completion functionality for gclient.

It's very basic, only subcommands.

If this would evolve, generation of _gclient should be automized (like a separate command
or some other tool.)

Review URL: http://codereview.chromium.org/546069

git-svn-id: svn://svn.chromium.org/chrome/trunk/tools/depot_tools@36521 0039d316-1c4b-4281-b951-d872f2087c98

zsh-goodies/README

+Various utilities for zsh.
+
+_gclient:
+  completion for gclient command.
+  To install add a path to zsh-goodies into your fpath variable, e.g.:
+    fpath=(<path to depot_tools>/zsh-goodies $fpath)

zsh-goodies/_gclient

+#compdef gclient
+
+_values commands \
+    cleanup \
+    config  \
+    diff    \
+    export  \
+    help    \
+    pack    \
+    status  \
+    sync    \
+    update  \
+    revert  \
+    runhooks\
+    revinfo