Review Board 1.7.22

Added SystemInfo::isLocalHost to check if a host name refers to the local host.

Review Request #4992 - Created May 3, 2012 and submitted

Alan Conway
astitcher, shuston
Need by the new HA work to avoid connections to self. 
- needs windows  implementation
- doesn't cover ipv6, neither does other Url handling code at this point
New unit test/SystemInfo.cpp. 
make check passes
Review request changed
Updated (May 7, 2012, 5 p.m.)
Updated with astitcher's comments.
Ship it!
Posted (May 7, 2012, 5:28 p.m.)