pgsql: Change the default setting for log_min_error_statement to ERROR.

Log Message:
-----------
Change the default setting for log_min_error_statement to ERROR. Per
recent discussion in which majority opinion was that this is a more
widely useful setting than the previous default of PANIC.

Modified Files:
--------------
pgsql/doc/src/sgml:
config.sgml (r1.95 -> r1.96)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/config.sgml.diff?r1=1.95&r2=1.96)
pgsql/src/backend/utils/misc:
guc.c (r1.358 -> r1.359)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/utils/misc/guc.c.diff?r1=1.358&r2=1.359)
postgresql.conf.sample (r1.198 -> r1.199)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/utils/misc/postgresql.conf.sample.diff?r1=1.198&r2=1.199)