Fix seg fault Frank Sweetser reports in regression testing

Fix seg fault Frank Sweetser reports in regression testing
     on his systems. The problem was that the original author of
     bsnprintf.c did not take into account the side effects of
     using ++x in the argument to a #define.

git-svn-id: https://bacula.svn.sourceforge.net/svnroot/bacula/branches/Branch-2.2@6124 91ce42f0-d328-0410-95d8-f526ca767f89