pgsql: Rearrange vacuum-related bits in PGPROC as a bitmask, to better

Log Message:
-----------
Rearrange vacuum-related bits in PGPROC as a bitmask, to better support
having several of them. Add two more flags: whether the process is
executing an ANALYZE, and whether a vacuum is for Xid wraparound (which
is obviously only set by autovacuum).

Sneakily move the worker's recently-acquired PostAuthDelay to a more useful
place.

Modified Files:
--------------
pgsql/src/backend/access/transam:
twophase.c (r1.36 -> r1.37)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/access/transam/twophase.c?r1=1.36&r2=1.37)
pgsql/src/backend/commands:
analyze.c (r1.109 -> r1.110)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/commands/analyze.c?r1=1.109&r2=1.110)
vacuum.c (r1.359 -> r1.360)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/commands/vacuum.c?r1=1.359&r2=1.360)
pgsql/src/backend/postmaster:
autovacuum.c (r1.62 -> r1.63)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/postmaster/autovacuum.c?r1=1.62&r2=1.63)
pgsql/src/backend/storage/ipc:
procarray.c (r1.35 -> r1.36)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/storage/ipc/procarray.c?r1=1.35&r2=1.36)
pgsql/src/backend/storage/lmgr:
proc.c (r1.194 -> r1.195)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/storage/lmgr/proc.c?r1=1.194&r2=1.195)
pgsql/src/include/storage:
proc.h (r1.100 -> r1.101)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/include/storage/proc.h?r1=1.100&r2=1.101)