Add "sendregion" command to GPU

This allows part of a buffer to be sent instead of the whole thing, meaning that driving digiscreen arrays can now be done with fewer commands and no temporary buffers.
This also greatly improves the speed of doing so, and I suppose also allows hardware-accelerated scrolling if your display is smaller than 64x64...

docs/gpu.txt

@@ -12,6 +12,7 @@ Example:
 		{command="send",buffer=0,channel="example"}
 	}
 	
+Invalid commands or commands with missing/invalid parameters will be ignored.
 
 Command: createbuffer
 ---------------------
@@ -33,6 +34,19 @@ Parameters:
 buffer [integer 0-7]: The buffer to send the contents of.
 channel [string]: The digilines channel to send the message on.
 
+Command: sendregion
+-------------------
+
+Sends part of the contents of a buffer to a digiscreen, rgblightstone panel, or other digilines device.
+
+Parameters:
+buffer [integer 0-7]: The buffer to send part of the contents of.
+channel [string]: The digilines channel to send the message on.
+x1 [integer 1-64]: The X position of the left side of the region to send.
+x2 [integer 1-64]: The X position of the right side of the region to send.
+y1 [integer 1-64]: The Y position of the top side of the region to send.
+y2 [integer 1-64]: The Y position of the bottom side of the region to send.
+
 Command: drawrect
 -----------------
 

gpu.lua

@@ -201,6 +201,33 @@ local function runcommand(pos,meta,command)
 		if type(buffer) == "table" then
 			digiline:receptor_send(pos,digiline.rules.default,command.channel,buffer)
 		end
+	elseif command.command == "sendregion" then
+		if type(command.buffer) ~= "number" or type(command.channel) ~= "string" then return end
+		local bufnum = math.floor(command.buffer)
+		if bufnum < 0 or bufnum > 7 then return end
+		local buffer = meta:get_string("buffer"..bufnum)
+		if string.len(buffer) == 0 then return end
+		buffer = minetest.deserialize(buffer)
+		if type(buffer) ~= "table" then return end
+		if type(command.x1) ~= "number" or type(command.x2) ~= "number" or type(command.y1) ~= "number" or type(command.x2) ~= "number" then return end
+		local x1 = math.min(64,math.floor(command.x1))
+		local y1 = math.min(64,math.floor(command.y1))
+		local x2 = math.min(64,math.floor(command.x2))
+		local y2 = math.min(64,math.floor(command.y2))	
+		if x1 < 1 or y1 < 1 or x2 < 1 or y2 < 1 then return end
+		x2 = math.min(x2,buffer.xsize)
+		y2 = math.min(y2,buffer.ysize)
+		if x1 > x2 or y1 > y2 then return end
+		local tempbuf = {}
+		for y=y1,y2,1 do
+			local dsty = y-y1+1
+			tempbuf[dsty] = {}
+			for x=x1,x2,1 do
+				local dstx = x-x1+1
+				tempbuf[dsty][dstx] = buffer[y][x]
+			end
+		end
+		digiline:receptor_send(pos,digiline.rules.default,command.channel,tempbuf)
 	elseif command.command == "drawrect" then
 		if type(command.buffer) ~= "number" or type(command.x1) ~= "number" or type(command.y1) ~= "number" or type(command.x2) ~= "number" or type(command.y2) ~= "number" then return end
 		local bufnum = math.floor(command.buffer)