Subzero: Fix asm (non-ELF) output files.

Subzero: Fix asm (non-ELF) output files.

In an earlier version of Subzero, the text output stream object was
stack-allocated within main.  A later refactoring moved its allocation
into a helper function, but it was still being stack-allocated, which
was bad when the helper function returned.

This change allocates the object via "new", which fixes that problem,
but reveals another problem: the raw_ostream object for some reason
doesn't finish writing everything to disk and yielding a truncated
output file.  This is solved in the style of the ELF streamer, by
using raw_fd_ostream instead.

BUG= none
R=kschimpf@google.com

Committed: https://gerrit.chromium.org/gerrit/gitweb?p=native_client/pnacl-subzero.git;a=commit;h=620ad732db0def93eee3928f9ebebe88b279f63d

[Jim Stichnoth, 2015-04-27 22:58:12]

stichnot@chromium.org changed reviewers:
+ jvoung@chromium.org, kschimpf@google.com, mtrofin@chromium.org

[Jim Stichnoth, 2015-04-27 22:58:38]

(The .h files are whitespace-only changes, thanks to "make format".)

[Karl, 2015-04-28 18:05:14]

lgtm

[Jim Stichnoth, 2015-04-28 21:12:23]

Committed patchset #1 (id:1) manually as
620ad732db0def93eee3928f9ebebe88b279f63d (presubmit successful).