Subzero: Change -asm-verbose output to print more useful info.

Subzero: Change -asm-verbose output to print more useful info.

Frame offsets for variables are emitted using a symbolic name based on the variable's name.  This makes it a bit easier to digest the asm code.

For example, if variable Foo gets an esp offset 24, asm like this:
  ... 24(%esp) ...
will instead be emitted like this:
  lv$Foo = 24
  ...
  ... lv$Foo(%esp) ...

Predecessor labels are printed for each basic block.

Loop nest depth is printed for each basic block.  (Would be nice if we had loop header info as well.)

BUG= none
R=jpp@chromium.org

Committed: https://gerrit.chromium.org/gerrit/gitweb?p=native_client/pnacl-subzero.git;a=commit;h=238b4c160169aea53c5ab87f40fd1d454f41e590

[Jim Stichnoth, 2015-10-01 06:51:53]

stichnot@chromium.org changed reviewers:
+ jpp@chromium.org, kschimpf@google.com, sehr@google.com

[John, 2015-10-01 14:26:59]

lgtm

[Jim Stichnoth, 2015-10-01 14:46:44]

Committed patchset #2 (id:20001) manually as
238b4c160169aea53c5ab87f40fd1d454f41e590 (presubmit successful).