remove unused portrait function from unit

This function was entirely unused, and deleting it allows us to
remove the "portrait.hpp" include from the unit.hpp header. (!)

src/unit.cpp

@@ -3086,20 +3086,6 @@ const std::string& unit::effect_image_mods() const{
 	return image_mods_;
 }
 
-const tportrait* unit::portrait(
-		const unsigned size, const tportrait::tside side) const
-{
-	BOOST_FOREACH(const tportrait& portrait, type().portraits() ) {
-		if(portrait.size == size
-				&& (side ==  portrait.side || portrait.side == tportrait::BOTH)) {
-
-			return &portrait;
-		}
-	}
-
-	return NULL;
-}
-
 void unit::remove_attacks_ai()
 {
 	if (attacks_left_ == max_attacks_) {

src/unit.hpp

@@ -21,7 +21,6 @@
 #include <boost/scoped_ptr.hpp>
 
 #include "formula_callable.hpp"
-#include "portrait.hpp"
 #include "resources.hpp"
 #include "unit_animation.hpp"
 #include "unit_types.hpp"
@@ -399,18 +398,6 @@ class unit
 	const std::string& effect_image_mods() const;
 	std::string image_mods() const;
 
-	/**
-	 * Gets the portrait for a unit.
-	 *
-	 * @param size                The size of the portrait.
-	 * @param side                The side the portrait is shown on.
-	 *
-	 * @returns                   The portrait with the wanted size.
-	 * @retval NULL               The wanted portrait doesn't exist.
-	 */
-	const tportrait* portrait(
-		const unsigned size, const tportrait::tside side) const;
-
 private:
 	void advance_to(const config &old_cfg, const unit_type &t,
 		bool use_traits);