add jump tables, constant pools and some trivial global

lowering stuff.  We can now compile hello world to:

_main:
	stm , 
	mov r7, sp
	sub sp, sp, #4
	mov r0, #0
	str r0, 
	ldr r0, 
	bl _printf
	ldr r0, 
	mov sp, r7
	ldm , 

Almost looks like arm code :)

llvm-svn: 84542