AArch64/ARM64: add support for :abs_gN_s: MOVZ modifiers

We only need assembly support, so it's fairly easy.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@207108 91177308-0d34-0410-b5e6-96231b3b80d8
AArch64/ARM64: support relocated ADR instruction

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@207109 91177308-0d34-0410-b5e6-96231b3b80d8
ARM64: support relocated "TBZ/TBNZ" instructions.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@207110 91177308-0d34-0410-b5e6-96231b3b80d8
AArch64/ARM64: allow negative addends, at least on ELF.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@207111 91177308-0d34-0410-b5e6-96231b3b80d8
AArch64/ARM64: enable remaining MC elf tests.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@207112 91177308-0d34-0410-b5e6-96231b3b80d8