Fixes teleporting leaving a unit halo.

The problem has been spotted by MJ999, who also provided this patch. I
haven't been able to reproduce the problem, but the invalidation
should have been there before.

changelog

@@ -7,6 +7,7 @@ Version 1.7.1+svn:
  * Miscellaneous and bugfixes:
    * Fixed language switch not affecting unit descriptions (bug #13827)
    * Fixed teleporting to impassable terrain (bug #13795)
+   * Fixed an issue where teleporting could leave a unit halo
 
 Version 1.7.1:
  * AI:

src/halo.cpp

@@ -307,6 +307,7 @@ void set_location(int handle, int x, int y)
 	const std::map<int,effect>::iterator itor = haloes.find(handle);
 	if(itor != haloes.end()) {
 		itor->second.set_location(x,y);
+		invalidated_haloes.insert(itor->first);
 	}
 }