Implement WieldMeshSceneNode which improves wield mesh rendering

- Don't create and cache an extruded mesh for every (non-node) item.
  Instead use a single one per image resolution.

- For cubic nodes reuse a single wield mesh too

- Improve lighting of the wielded item

- Increase far value of wield mesh scene camera, fixes #1770

- Also includes some minor refactorings of Camera and GenericCAO.

src/localplayer.cpp

@@ -48,6 +48,7 @@ LocalPlayer::LocalPlayer(IGameDef *gamedef, const char *name):
 	last_animation(NO_ANIM),
 	hotbar_image(""),
 	hotbar_selected_image(""),
+	light_color(255,255,255,255),
 	m_sneak_node(32767,32767,32767),
 	m_sneak_node_exists(false),
 	m_old_node_below(32767,32767,32767),