qapi: merge QInt and QFloat in QNum

We would like to use a same QObject type to represent numbers, whether
they are int, uint, or floats. Getters will allow some compatibility
between the various types if the number fits other representations.

Add a few more tests while at it.

Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Message-Id: <20170607163635.17635-7-marcandre.lureau@redhat.com>
Reviewed-by: Markus Armbruster <armbru@redhat.com>
[parse_stats_intervals() simplified a bit, comment in
test_visitor_in_int_overflow() tidied up, suppress bogus warnings]
Signed-off-by: Markus Armbruster <armbru@redhat.com>
diff --git a/monitor.c b/monitor.c
index fcf4fad..3c369f4 100644
--- a/monitor.c
+++ b/monitor.c
@@ -2974,7 +2974,7 @@
                     monitor_printf(mon, "Unknown unit suffix\n");
                     goto fail;
                 }
-                qdict_put(qdict, key, qfloat_from_double(val));
+                qdict_put(qdict, key, qnum_from_double(val));
             }
             break;
         case 'b':