Minor changes to instruction trace output.

Minor changes to instruction trace output.

arch/alpha/isa_desc:
    A few disassembly changes to make it easier to compare with old machine.def traces:
    - Make lds prefetches print f31 instead of r31 as dest.
    - Don't print mode suffixes on FP if SS_COMPATIBLE_DISASSEMBLY
cpu/exetrace.cc:
    Left-justify instruction in field, and increase width by 1.

--HG--
extra : convert_revision : 9ffd56728f1bb772aa3ccda5f027b93d4c3a4135