Variable Size Regions! Support for prehash RegionSizeX and large patches. (WIP)

Mostly from Ukando, tweaked a bit to be cleaner, and a little less dramatic.

decode_patch_header now takes a bool optionally, as third argument.
_PREHASH_RegionSizeX is the only used of the two _PREHASH_RegionSize*.
llsurface.cpp: Copy the connectNeighbor for variable size regions almost directly from Ukando
llsurfacepatch.cpp: Patch code from ukando and voodoo.
Changed hardcoded 256 constants and such to width functions in: llglsandbox.cpp, llsurface.cpp, llviewerregion.cpp, llviewerparcelmanager, llviewerparcelmgr.cpp, llvowater.cpp, llworld.cpp
Use region specific width in: llagent.cpp, llglsandbox.cpp, llmanip.cpp, llmanipscale.cpp, llpanelobject.cpp, llviewerbject.cpp, llwind.cpp
Use 256 in llnetmap.cpp in places...
llfloaterregioninfo.cpp: Aurora grid has wacky textures.
Add LLViewerParcelMgr::widthUpdate() for updating mParcelsPerEdge given a region's width. Used in llstartup now.
Add LLWorld::setWidth() for getting a region's size from LLMessageSystem pointers and setting mWidth and mWidthInMeters, accordingly. Called in llviewermessage.cpp as well.

indra/newview/llstartup.cpp

@@ -4197,7 +4197,10 @@ bool process_login_success_response(std::string& password)
 		U32 region_y = strtoul(region_y_str.c_str(), NULL, 10);
 		gFirstSimHandle = to_region_handle(region_x, region_y);
 	}
-	
+
+	text = response["region_size_x"].asString();
+	if (!text.empty()) LLViewerParcelMgr::getInstance()->widthUpdate(atoi(text.c_str()));
+
 	const std::string look_at_str = response["look_at"];
 	if (!look_at_str.empty())
 	{