Don't copy util functions in client.c

This requires moving croak() to logging.c and avoiding use
of log functions in util.c.

logging.c

@@ -214,3 +214,19 @@ LOG_GoDaemon(void)
 }
 
 /* ================================================== */
+/* Force a core dump and exit without doing abort() or assert(0).
+   These do funny things with the call stack in the core file that is
+   generated, which makes diagnosis difficult. */
+
+int
+croak(const char *file, int line, const char *msg)
+{
+  int a;
+  LOG(LOGS_ERR, LOGF_Util, "Unexpected condition [%s] at %s:%d, core dumped",
+      msg, file, line);
+  a = * (int *) 0;
+  return a; /* Can't happen - this stops the optimiser optimising the
+               line above */
+}
+
+/* ================================================== */