[dwarfdump] Make debug_frame dump actually useful.

This adds support for pretty-printing instruction operands. The new
output looks like:

00000000 00000010 ffffffff CIE
  Version:               1
  Augmentation:
  Code alignment factor: 1
  Data alignment factor: -4
  Return address column: 8

  DW_CFA_def_cfa:  reg4 +4
  DW_CFA_offset:  reg8 -4
  DW_CFA_nop:
  DW_CFA_nop:

00000014 00000010 00000000 FDE cie=00000000 pc=00000000...00000022
  DW_CFA_advance_loc:  3
  DW_CFA_def_cfa_offset:  +12
  DW_CFA_nop:

llvm-svn: 230551