pgsql: Factor out lock cleanup code that is needed in several places in

Log Message:
-----------
Factor out lock cleanup code that is needed in several places in lock.c.
Also, remove the rather useless return value of LockReleaseAll.  Change
response to detection of corruption in the shared lock tables to PANIC,
since that is the only way of cleaning up fully.
Originally an idea of Heikki Linnakangas, variously hacked on by
Alvaro Herrera and Tom Lane.

Modified Files:
--------------
    pgsql/contrib/userlock:
        user_locks.c (r1.16 -> r1.17)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/contrib/userlock/user_locks.c.diff?r1=1.16&r2=1.17)
    pgsql/src/backend/storage/lmgr:
        lock.c (r1.151 -> r1.152)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/storage/lmgr/lock.c.diff?r1=1.151&r2=1.152)
    pgsql/src/include/storage:
        lock.h (r1.85 -> r1.86)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/include/storage/lock.h.diff?r1=1.85&r2=1.86)