arm: enable all tests

ARM functionality is now completely working.
(Or if it's not, we'll fix it.)

R=ken2
CC=golang-dev
https://golang.org/cl/2738041
diff --git a/src/pkg/runtime/arm/asm.s b/src/pkg/runtime/arm/asm.s
index b9e7106..dd317cc 100644
--- a/src/pkg/runtime/arm/asm.s
+++ b/src/pkg/runtime/arm/asm.s
@@ -64,6 +64,8 @@
 TEXT mainstart(SB),7,$4
 	BL	mainĀ·init(SB)
 	BL	initdone(SB)
+	EOR	R0, R0
+	MOVW	R0, 0(R13)
 	BL	mainĀ·main(SB)
 	MOVW	$0, R0
 	MOVW	R0, 4(SP)
@@ -84,7 +86,7 @@
 	BL	_sfloat(SB)
 
 TEXT	breakpoint(SB),7,$0
-	BL	abort(SB)
+	// no breakpoint yet; let program exit
 	RET
 
 /*