Fix two bugs regarding stale SIS messages, from Kruzen

When entering Hyperspace on Auto-Pilot, or are intercepted by
neutral or hostile alien ships during Auto-Pilot, the text at the
top of the screen doesn't update properly until the status
would need to change. This corrects the times when DrawSisMessage
is called to keep that up-to-date as needed.

This patch was backported from the Mega-Mod.

sc2/ChangeLog

@@ -62,6 +62,7 @@
   current Sourceforge installs; generic support now available for both HTTPS
   and automatic redirection to mirrors - Michael
 - Fixed MSYS resource script compilation/linking, from Ala-lala
+- Fixed stale main-screen header text displays, from Kruzen
 
 0.7.1:
 - New SDL2 backend for modern operating systems - Michael

sc2/src/uqm/encount.c

@@ -326,6 +326,7 @@ InitEncounter (void)
 		t.CharCount = (COUNT)~0;
 		font_DrawText (&t);
 	}
+	DrawSISMessage (NULL);
 
 	s.origin.x = SIS_SCREEN_WIDTH >> 1;
 	s.origin.y = SIS_SCREEN_HEIGHT >> 1;

sc2/src/uqm/hyper.c

@@ -349,7 +349,10 @@ LoadHyperspace (void)
 			RepairSISBorder ();
 		}
 	}
-	DrawSISMessage (NULL);
+	if (!(GLOBAL (autopilot.x) != ~0 && GLOBAL (autopilot.y) != ~0))
+	{
+		DrawSISMessage (NULL);
+	}
 
 	SetContext (RadarContext);
 	SetContextBackGroundColor (