initial commit of the arm port

this port assumes eabi calling conventions, eabi linux syscall
convention, and presence of the kernel helpers at 0xffff0f?0 needed
for threads support. otherwise it makes very few assumptions, and the
code should work even on armv4 without thumb support, as well as on
systems with thumb interworking. the bits headers declare this a
little endian system, but as far as i can tell the code should work
equally well on big endian.

some small details are probably broken; so far, testing has been
limited to qemu/aboriginal linux.

src/setjmp/arm/longjmp.s

@@ -0,0 +1,15 @@
+.global _longjmp
+.global longjmp
+.type _longjmp,%function
+.type longjmp,%function
+_longjmp:
+longjmp:
+	mov ip,r0
+	movs r0,r1
+	moveq r0,#1
+	ldmia ip!, {v1,v2,v3,v4,v5,v6,sl,fp}
+	ldr sp,[ip],#4
+	ldr lr,[ip],#4
+	tst lr,#1
+	moveq pc,lr
+	bx lr

src/setjmp/arm/setjmp.s

@@ -0,0 +1,17 @@
+.global __setjmp
+.global _setjmp
+.global setjmp
+.type __setjmp,%function
+.type _setjmp,%function
+.type setjmp,%function
+__setjmp:
+_setjmp:
+setjmp:
+	mov ip,r0
+	stmia ip!,{v1,v2,v3,v4,v5,v6,sl,fp}
+	mov r2,sp
+	stmia ip!,{r2,lr}
+	mov r0,#0
+	tst lr,#1
+	moveq pc,lr
+	bx lr