pgsql: Reduce size of critial section during vacuum full, critical

Log Message:
-----------
Reduce size of critial section during vacuum full, critical
sections now isn't nested. All user-defined functions now is
called outside critsections. Small improvements in WAL
protocol.

TODO: improve XLOG replay

Modified Files:
--------------
pgsql/src/backend/access/gist:
gist.c (r1.134 -> r1.135)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/access/gist/gist.c.diff?r1=1.134&r2=1.135)
gistutil.c (r1.11 -> r1.12)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/access/gist/gistutil.c.diff?r1=1.11&r2=1.12)
gistvacuum.c (r1.20 -> r1.21)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/access/gist/gistvacuum.c.diff?r1=1.20&r2=1.21)
gistxlog.c (r1.16 -> r1.17)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/access/gist/gistxlog.c.diff?r1=1.16&r2=1.17)
pgsql/src/include/access:
gist_private.h (r1.13 -> r1.14)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/include/access/gist_private.h.diff?r1=1.13&r2=1.14)