Connect Engine: removed "--give--" entry from controller options

This was basically used to separate players from the general controller options. In the GUI1 dialog it
was unselectable. I never got around to implementing that in the GUI2 dialog, but regardless, it doesn't
look great in the menu so I'm removing it. Plus, since the dropdowns are GUI2, we could apply different
text formatting to denote players if we wanted.

src/game_initialization/connect_engine.cpp

@@ -1034,7 +1034,6 @@ config side_engine::new_config() const
 		res["name"] = desc;
 	}
 
-	assert(controller_ != CNTR_LAST);
 	if(controller_ == CNTR_COMPUTER && allow_player_) {
 		// Do not import default ai cfg otherwise - all is set by scenario config.
 		res.add_child_at("ai", config {"ai_algorithm", ai_algorithm_}, 0);
@@ -1286,7 +1285,6 @@ void side_engine::update_controller_options()
 	}
 
 	// Connected users.
-	add_controller_option(CNTR_LAST, _("--give--"), "human");
 	for(const std::string& user : parent_.connected_users()) {
 		add_controller_option(parent_.default_controller_, user, "human");
 	}
@@ -1317,9 +1315,6 @@ void side_engine::update_current_controller_index()
 bool side_engine::controller_changed(const int selection)
 {
 	const ng::controller selected_cntr = controller_options_[selection].first;
-	if(selected_cntr == CNTR_LAST) {
-		return false;
-	}
 
 	// Check if user was selected. If so assign a side to him/her.
 	// If not, make sure that no user is assigned to this side.

src/game_initialization/connect_engine.hpp

@@ -31,7 +31,6 @@ enum controller {
 	CNTR_COMPUTER,
 	CNTR_EMPTY,
 	CNTR_RESERVED,
-	CNTR_LAST
 };
 
 class connect_engine;