WAL Bootstrap/Startup/Shutdown committed...

gmake clean + initdb (also changed) required.

WAL still doesn't anything but eats 16Mb disk space on bootstrap -:)

Data base system shutdown is changed!

Now, after receiving SIGTERM, postmaster disallows new
connections but let active backend to end their works
and shutdown data base only after all of them terminated
(by client request) - Smart Shutdown.

SIGINT: postmaster disallows new connections,
sends all active backends SIGTERM (abort+exit),
waits for children exits and shutdowns data base
- Fast Shutdown.

SIGQUIT: postmaster terminates children with SIGUSR1
and exits (without shutdowning data base)
- Immediate Shutdown (results in recovery on startup).

I started to clean up backend initialization code: MUST use
locking when read catalog relations and setup MyProc before
acquiring any (except for ProcStructLock) spinlocks.

Also, now FATAL is ERROR + exit.

Vadim