pgsql: Cause the output from debug_print_parse, debug_print_rewritten,

Log Message:
-----------
Cause the output from debug_print_parse, debug_print_rewritten, and
debug_print_plan to appear at LOG message level, not DEBUG1 as historically.
Make debug_pretty_print default to on. Also, cause plans generated via
EXPLAIN to be subject to debug_print_plan. This is all to make
debug_print_plan a reasonably comfortable substitute for the former behavior
of EXPLAIN VERBOSE.

Modified Files:
--------------
pgsql/doc/src/sgml:
config.sgml (r1.185 -> r1.186)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/config.sgml?r1=1.185&r2=1.186)
pgsql/src/backend/commands:
explain.c (r1.177 -> r1.178)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/backend/commands/explain.c?r1=1.177&r2=1.178)
pgsql/src/backend/tcop:
postgres.c (r1.555 -> r1.556)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/backend/tcop/postgres.c?r1=1.555&r2=1.556)
pgsql/src/backend/utils/misc:
guc.c (r1.466 -> r1.467)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/backend/utils/misc/guc.c?r1=1.466&r2=1.467)
postgresql.conf.sample (r1.244 -> r1.245)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/backend/utils/misc/postgresql.conf.sample?r1=1.244&r2=1.245)