Improvements to the ARM64 disassembler.

This contains three changes:
- Use register aliases in the disassembly.
- When loading from a literal pool, show what is being loaded.
- Disassemble using absolute addresses on ARM64.
  This ensures that addresses disassembled are coherent with instruction
  location addresses shown.

Examples of disassembled instructions before and after the changes:

Before:
  movz w17, #0x471f
  ldr d9, pc+736 (addr 0x72690d50)

After:
  movz wip1, #0x471f
  ldr d9, pc+736 (addr 0x72690d50) (-745.133)

Change-Id: I72fdc160fac26f74126921834f17a581c26fd5d8