Adds test program with screen clear routine.

libvm/test.asm

@@ -0,0 +1,38 @@
+;
+; Simple memory transform-and-copy program
+;
+_start:
+	push 0xFFFF00
+	cpget
+	jmp @cls
+	push 0x00FFFF
+	cpget
+	jmp @cls
+	jmp @_start
+	syscall
+
+cls:
+	bpget
+	spget
+	bpset
+	push 0
+cls_copy:
+	dup
+	cmp 1228800 ; 640*480*4 screen size
+	[ex(z)=1] jmp @cls_stop
+	
+	get -2 ; Get color argument
+	get 1  ; Get iterator
+	[i0:arg] add 4096 ; Add screen buffer offset
+	
+	storei [ci:2] ; Write 32bit value
+	
+	; Increase counter
+	[i0:arg] add 4
+	jmp @cls_copy
+
+cls_stop:
+	bpget
+	spset
+	bpset
+	ret