Extend x64 disassembler with ability to decode and output recorded comments.
Example output (currently comments are emitted only by flow graph compiler at block/instruction boundaries, once instruction printing is refactored and supports printing into buffer simple "instruction" comment will be replaced with the actual IL construct):
;; B0
;; B1
;; instruction
0x007f0fff812525 00000055 49 bb 21 00 b4 04 10 mov $0x7f1004b40021,%r11
0x007f0fff81252c 0000005c 7f 00 00
0x007f0fff81252f 0000005f 41 53 push %r11
R=srdjan@google.com
Review URL: https://chromiumcodereview.appspot.com//10407019
git-svn-id: https://dart.googlecode.com/svn/branches/bleeding_edge/dart@7723 260f80e4-7a28-3924-810f-c04153c831b5
vegorov@google.com