-LLCached[COA]Control can now be static const. Use for readonly access.

-const'd all readonly LLCached[COA]Controls to prevent altering by mistake.
-added get() accessor to LLCached[COA]Controls to return cached type explicitly without manual casts.
-added missing operators to LLCachedCOAControl
-Converted a few more settings to LLCached[COA]Control
-Fixed LLColor4U -> LLSD -> LLColor4 problems in LLCachedControl

Ascent functionality fixes:
-Tag coloring pulled out of getClientInfo(Redundant. idleUpdateNameTag already handled it)
--Tag and color substituted at render-time. Simple boolean logic. Neglible perf penalty.
-Fixed llinfos spam if AscentShowSelfTagColor = false
-Client tag updated less superfluously

indra/newview/lldrawpoolterrain.cpp

@@ -209,7 +209,7 @@ void LLDrawPoolTerrain::render(S32 pass)
 	}
 
 	// Special-case for land ownership feedback
-	static LLCachedControl<bool> show_parcel_owners("ShowParcelOwners",false);
+	static const LLCachedControl<bool> show_parcel_owners("ShowParcelOwners",false);
 	if (show_parcel_owners)
 	{
 		if (mVertexShaderLevel > 1)