rdar://problem/11598332

The output of 'register read' should be prettier.
Modify RegisterValue::Dump() to take an additional parameter:

    uint32_t reg_name_right_align_at

which defaults to 0 (i.e., no alignment at all).  Update the 'register read' command impl to pass 8
as the alignment to RegisterValue::Dump() method.  If more sophisticated scheme is desired, we will
need to introduce an additional command option to 'register read' later on.

llvm-svn: 158039