Thread: pgsql: Use CRITICAL_SECTION instead of Mutexes for thread-locking in

Log Message:
-----------
Use CRITICAL_SECTION instead of Mutexes for thread-locking in libpq on
Windows, for better performance.

Per suggestion from Andrew Chernow, but not his patch since the underlying
code was changed to deal with return values.

Modified Files:
--------------
    pgsql/src/interfaces/libpq:
        pthread-win32.c (r1.16 -> r1.17)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/interfaces/libpq/pthread-win32.c?r1=1.16&r2=1.17)
    pgsql/src/port:
        pthread-win32.h (r1.4 -> r1.5)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/port/pthread-win32.h?r1=1.4&r2=1.5)