SIGINT is handled in funny ways on windows, which could lead to problems when
Control-C was pressed in the client during a long-running query.  Now Control-C
during a query aborts that query (by sending KILL to the server on a second
connexion), while Control-C outside of a running query terminates the client.


client/mysql.cc:
  Bug#17926: mysql.exe crashes when ctrl-c is pressed in windows
  
  Rather than tear down the client right away, open a second connexion to server
  on SIGINT and send a KILL for the first connexion.  Only if we receive another
  SIGINT before the KILL goes through (or if no query was running in the first
  place) do we terminate the client.