Refactor player's eye position coding

Collect the player's eye position coding in a Player method, and
use it in client to pass the eye position information to the game.

src/player.h

@@ -67,6 +67,14 @@ public:
 		return floatToInt(m_position + v3f(0,BS+BS/2,0), BS);
 	}
 
+	v3f getEyePosition()
+	{
+		// This is at the height of the eyes of the current figure
+		// return m_position + v3f(0, BS+BS/2, 0);
+		// This is more like in minecraft
+		return m_position + v3f(0,BS+(5*BS)/8,0);
+	}
+
 	virtual void setPosition(const v3f &position)
 	{
 		m_position = position;