Add more random-number noise collection calls.

Mostly on the Unix side: there are lots of places the Windows code was
collecting noise that the corresponding Unix/GTK code wasn't bothering
to, such as mouse movements, keystrokes and various network events.
Also, both platforms had forgotten to collect noise when reading data
from a pipe to a local proxy process, even though in that
configuration that's morally equivalent to the network packet timings
that we'd normally be collecting from.

unix/uxpterm.c

@@ -14,6 +14,9 @@ const bool dup_check_launchable = false; /* no need to check host name
                                           * in conf */
 const bool use_pty_argv = true;
 
+/* gtkwin.c will call this, and in pterm it's not needed */
+void noise_ultralight(unsigned long data) { }
+
 const struct BackendVtable *select_backend(Conf *conf)
 {
     return &pty_backend;