ART: Enable the use of relative addresses in the arm64 disassembler.

Also, only keep register aliases for the link register 'lr' and the
thread register 'tr' in the arm64 disassembler. Other aliases are not
very important, and this way we don't have to provide aliases
specialised for Quick or Optimizing.

Change-Id: Ie7a04910f0c587710a0cf2648203d7e89eab5d1f