Cancel a dbclient password prompt if the user presses ctrl-c.

Enter still has to be pressed since glibc blocks ctrl-c in getpass()

--HG--
extra : convert_revision : 1c8128fba89431f2460dd5914f0614850d529b76

auth.h

@@ -52,6 +52,7 @@ void cli_pubkeyfail();
 void cli_auth_password();
 int cli_auth_pubkey();
 void cli_auth_interactive();
+char* getpass_or_cancel();
 
 
 #define MAX_USERNAME_LEN 25 /* arbitrary for the moment */