Fix unused variable and parameter warnings from gcc

Deals with the following warnings (errors in strict mode) by removing
the offending code and dropping a parameter name, respectively.

  src/pathfind/teleport.cpp: In member function ‘void pathfind::teleport_group::get_teleport_pair(pathfind::teleport_pair&, const unit&, bool) const’:
  src/pathfind/teleport.cpp:70:12: error: variable ‘units’ set but not used [-Werror=unused-but-set-variable]

  src/pathfind/teleport.cpp:66:16: error: unused parameter ‘ignore_units’ [-Werror=unused-parameter]

iceiceice, you probably should take a look at this.

src/pathfind/teleport.cpp

@@ -63,16 +63,11 @@ teleport_group::teleport_group(const vconfig& cfg, bool reversed) : cfg_(cfg.get
 void teleport_group::get_teleport_pair(
 		  teleport_pair& loc_pair
 		, const unit& u
-		, const bool ignore_units) const
+		, const bool /*ignore_units*/) const
 {
 	const map_location &loc = u.get_location();
 	static unit_map empty_unit_map;
-	unit_map *units;
-	if (ignore_units) {
-		units = &empty_unit_map;
-	} else {
-		units = resources::units;
-	}
+
 	vconfig filter(cfg_.child_or_empty("filter"), true);
 	vconfig source(cfg_.child_or_empty("source"), true);
 	vconfig target(cfg_.child_or_empty("target"), true);