add jump tables, constant pools and some trivial global

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 :)

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@84542 91177308-0d34-0410-b5e6-96231b3b80d8