Added -Wformat=2 - checks for some safety/security violations on format strings.
Added -Wformat=2 - checks for some safety/security violations on format strings.

mckelvin/libmemcached,mckelvin/libmemcached,tony2001/libmemcached,tony2001/libmemcached,tony2001/libmemcached,mckelvin/libmemcached