STORM-971 FIXED Disable the 'Stop Tracking' menu item in Mini-map floater when...

STORM-971 FIXED Disable the 'Stop Tracking' menu item in Mini-map floater when tracking gets stopped.
- Removed the menu from LLFloaterMap (the mini-map floater)
  that had conflicted with the one in the LLNetMap widget.
- Fixed updating of the "Stop Tracking" menu item; moved that code
  out of draw() to avoid excessive updates.
- Preventively fixed LLTracker::isTracking() to return strictly 1 or 0
  (BOOL is known to cause hard-to-debug side effects with values > 1
  because it's essentially just an int and thus doesn't enforce
  any limitations on the value).