pgbouncer - pgbouncer: Clean warning flags for newer gccs.

Log Message:
-----------
Clean warning flags for newer gccs.

-Wformat=2 should turn on all useful format flags.

-Wstrict-overflow is too noisy, lower level is on by default.

Modified Files:
--------------
pgbouncer:
configure.ac (r1.61 -> r1.62)
(http://cvs.pgfoundry.org/cgi-bin/cvsweb.cgi/pgbouncer/pgbouncer/configure.ac?r1=1.61&r2=1.62)