loader: Move drawer.lua over to gfx table.

Drawer.lua is the only bit of lua code in the base that uses any of the
functons moved from the loader table to the gfx table. Move the main
code to using the gfx dispatch. Add compat code for running on old
loaders that creates the newer-style gfx table with the term_* functions
we call in it populated. This will even work on the super old versions
of the loader that don't have them (we'll still skip using them).

Sponsored by:		Netflix
Reviewed by:		kevans
Differential Revision:	https://reviews.freebsd.org/D43908

stand/lua/drawer.lua

@@ -47,6 +47,19 @@ local frame_size
 local default_shift
 local shift
 
+-- Make this code compatible with older loader binaries. We moved the term_*
+-- functions from loader to the gfx. if we're running on an older loader that
+-- has these functions, create aliases for them in gfx. The loader binary might
+-- be so old as to not have them, but in that case, we want to copy the nil
+-- values. The new loader will provide loader.* versions of all the gfx.*
+-- functions for backwards compatibility, so we only define the functions we use
+-- here.
+if gfx == nil then
+	gfx = {}
+	gfx.term_drawrect = loader.term_drawrect
+	gfx.term_putimage = loader.term_putimage
+end
+
 local function menuEntryName(drawing_menu, entry)
 	local name_handler = menu_name_handlers[entry.entry_type]
 
@@ -225,8 +238,8 @@ local function drawframe()
 	x = x + shift.x
 	y = y + shift.y
 
-	if core.isFramebufferConsole() and loader.term_drawrect ~= nil then
-		loader.term_drawrect(x, y, x + w, y + h)
+	if core.isFramebufferConsole() and gfx.term_drawrect ~= nil then
+		gfx.term_drawrect(x, y, x + w, y + h)
 		return true
 	end
 
@@ -312,9 +325,9 @@ local function drawbrand()
 	end
 
 	if core.isFramebufferConsole() and
-	    loader.term_putimage ~= nil and
+	    gfx.term_putimage ~= nil and
 	    branddef.image ~= nil then
-		if loader.term_putimage(branddef.image, 1, 1, 0, 7, 0)
+		if gfx.term_putimage(branddef.image, 1, 1, 0, 7, 0)
 		then
 			return true
 		end
@@ -363,14 +376,14 @@ local function drawlogo()
 	end
 
 	if core.isFramebufferConsole() and
-	    loader.term_putimage ~= nil and
+	    gfx.term_putimage ~= nil and
 	    logodef.image ~= nil then
 		local y1 = 15
 
 		if logodef.image_rl ~= nil then
 			y1 = logodef.image_rl
 		end
-		if loader.term_putimage(logodef.image, x, y, 0, y + y1, 0)
+		if gfx.term_putimage(logodef.image, x, y, 0, y + y1, 0)
 		then
 			return true
 		end