[freeciv-ai] patch/rfc: wrap activity

["Per I. Mathisen" <per@xxxxxxxxxxx>]

This is the essential wrapper for retaining fortification status, taken
from massive ai patch. Shout if you think this is wrong, otherwise I will
commit along with the necessary wrapping changes elsewhere in the code.

  - Per

diff -u -r1.62 aitools.c

+/**************************************************************************
+  Gate all changes to unit activities through here to enforce sanity
+
+  FIXME: packetify request
++**************************************************************************/
+void ai_unit_new_activity(struct unit *punit, enum unit_activity task)
+{
+  if (punit->activity == task) {
+    return; /* useless */
+  }
+  if (punit->activity == ACTIVITY_FORTIFIED && task == ACTIVITY_FORTIFYING) {
+    return; /* worse than useless */
   }
+  handle_unit_activity_request(punit, task);
 }