Fixed failing test cases and compiler warnings found by buildbot

- Added some extra command to rpl_start_stop to ensure that the
  IO thread has connected to the master before we shut down the server.
- if signal returns signalhandler_t, use this with the alarm code
- Added missing tests to sys_vars
- Fixed some possible overflow bugs in tabxml.cpp

storage/connect/value.cpp

@@ -2666,7 +2666,7 @@ bool DTVAL::SetValue_pval(PVAL valp, bool chktype)
 /***********************************************************************/
 bool DTVAL::SetValue_char(char *p, int n)
   {
-  bool rc;
+  bool rc= 0;
 
   if (Pdtp) {
     char *p2;