pgsql: Revert temporary patch that made synchronous_commit default to

Log Message:
-----------
Revert temporary patch that made synchronous_commit default to OFF.

Modified Files:
--------------
    pgsql/doc/src/sgml:
        config.sgml (r1.143 -> r1.144)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/config.sgml?r1=1.143&r2=1.144)
    pgsql/src/backend/utils/misc:
        guc.c (r1.418 -> r1.419)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/utils/misc/guc.c?r1=1.418&r2=1.419)
    pgsql/src/tools:
        RELEASE_CHANGES (r1.74 -> r1.75)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/tools/RELEASE_CHANGES?r1=1.74&r2=1.75)