uint to_string() fixes for centos

Fixes compilation errors on CentOS. It's probably incorrect for other platforms.

Linux prod-solrmarge20.ma01.shuttercorp.net 2.6.32-431.el6.x86_64 #1 SMP Fri Nov 22 03:15:09 UTC 2013 x86_64 x86_64 x86_64 GNU/Linux
g++ (GCC) 4.4.7 20120313 (Red Hat 4.4.7-11)