This fixes an issue we are seeing with VSTU debgugging in Unity. (mono#7634)

process_breakpoint() will process breakpoint, stepping, and method
exit/entry events all at the same time when checking a sequence point.
So, if there is is a breakpoint and a stepping event at the same time,
the debugger agent will suspend the current thread twice, which means
you have to click the step button in the debugger client twice on that
line.  Considering only one of these events at a time seems to fix
the issue without breaking any current unit tests or showing any other
noticeable issues in testing.

Author: brianradunity

mono/mini/debugger-agent.c

@@ -5531,9 +5531,9 @@ process_breakpoint (DebuggerTlsData *tls, gboolean from_signal)
 
 	if (ss_reqs->len > 0)
 		ss_events = create_event_list (EVENT_KIND_STEP, ss_reqs, ji, NULL, &suspend_policy);
-	if (bp_reqs->len > 0)
+	else if (bp_reqs->len > 0)
 		bp_events = create_event_list (EVENT_KIND_BREAKPOINT, bp_reqs, ji, NULL, &suspend_policy);
-	if (kind != EVENT_KIND_BREAKPOINT)
+	else if (kind != EVENT_KIND_BREAKPOINT)
 		enter_leave_events = create_event_list (kind, NULL, ji, NULL, &suspend_policy);
 
 	mono_loader_unlock ();