Fix/callsite incorrect

I had the problem with callsite on certain x64 systems.. It reported NLog.LoggerImpl.Write instead of the actual callsite.. This fixes the problem for me:


*Before:*
2014-05-01 15:01:39.5402|33|Info|NLog.LoggerImpl.Write|User '' () logged in from xxx.xxx.xxx.xxx

*After:*
2014-05-01 15:03:02.7554|28|Info|Login.LoginUser|User '' () logged in from xxx.xxx.xxx.xxx