ovsdb-doc: Add ovsdb-doc to distribution tar ball.

ovsdb-doc: Add ovsdb-doc to distribution tar ball.

Certain platforms like xenserver do not have the latest
python libraries that are needed by ovsdb-doc (which in-turn
creates ovs-vswitchd.conf.db.5). When we run 'make dist' and
copy over the tar ball to xenserver ddk environemt, we
already include ovs-vswitchd.conf.db.5. But the absence of
ovsdb-doc results in an attempt to regenerate ovs-vswitchd.conf.db.5
and that fails because of the missing python libraries.

Instead of producing ovsdb-doc from ovsdb-doc.in dynamically, we
statically provide ovsdb-doc and pass on the version information
to it through the command line option --version.

Signed-off-by: Gurucharan Shetty <gshetty@nicira.com>
Acked-by: Ben Pfaff <blp@nicira.com>