new lock structure names

I have renamed most of the variables/structures in
backend/storage/lmgr/lock.c. The old names were very confusing.

Names like LOCKTAB, LOCKCTL, ltable, ntypes, AllTables, locktype,
LockTableInit, tableId, tableID, lockName are gone. There are two
primary items in lock.c. One is the locking method. Currently we only
support multi-level locks. The second is lock mode (read/write). These
were very unclear in the code. Now, I can understand what is happening,
and I hope others can too.

I have attatched the contents of the README in that directory, to show
that someone in 1992 also agrees with me, in case some want to complain
that I changed some variable names.

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This file is an attempt to save me (and future code maintainers) some
time and a lot of headaches. The existing lock manager code at the time
of this writing (June 16 1992) can best be described as confusing. The
complexity seems inherent in lock manager functionality, but variable
names chosen in the current implementation really confuse me everytime
I have to track down a bug. Also, what gets done where and by whom isn't
always clear....

--
Bruce Momjian | 830 Blythe Avenue
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