Log sources are stored in LogLevel order to speed up log calls.

By sorting the log sources by LogLevel the number of calls to Log will be cut down when low priority messages are logged (e.g. XLOG_DEBUG and XLOG_INFO). Every log source does not need to be checked since they are ordered; once one log source has too high of a priority (e.g. XLOG_ERROR) then all log sources after it will have too high of a priority.