Rename minidump_test_util.* to minidump_file_writer_test_util.*

Rename minidump_test_util.* to minidump_file_writer_test_util.*.

This is in line with the other new minidump_*_test_util files, namely,
the “context” and “memory” ones. minidump_file_writer_test_util.*
provides VerifyMinidumpHeader(), which is used to validate the
MINIDUMP_HEADER at the beginning of a minidump file, as written by
MinidumpFileWriter.

TEST=minidump_test
R=rsesek@chromium.org

Committed: https://chromium.googlesource.com/crashpad/crashpad/+/c182be95a2498ddbe0efa6b8ba27a95547ab230c

[Mark Mentovai, 2014-10-09 19:34:42]

mark@chromium.org changed reviewers:
+ rsesek@chromium.org

[Robert Sesek, 2014-10-09 21:06:48]

LGTM

[Mark Mentovai, 2014-10-09 21:08:14]

Committed patchset #1 (id:1) manually as
c182be95a2498ddbe0efa6b8ba27a95547ab230c (presubmit successful).