Switch scoped_ptr.h to a compatible google3 implementation.

This is Chromium's base/memory/scoped_ptr.h at r98718, which split off
from the google3 version at a later point than Breakpad's copy. It is a
drop in replacement and the only changes are:
- removal of WARN_UNUSED_RESULT.
- moving it into the google_breakpad namespace.

BUG=534
R=mark@chromium.org

Review URL: https://breakpad.appspot.com/964002

git-svn-id: http://google-breakpad.googlecode.com/svn/trunk@1265 4c0a9323-5329-0410-9bdc-e9ce6186880e
Use a proper ignore_result() to fix a ftruncate warn_unused_result warning with GCC 4.8.

BUG=492
R=mark@chromium.org

Review URL: https://breakpad.appspot.com/944003

git-svn-id: http://google-breakpad.googlecode.com/svn/trunk@1266 4c0a9323-5329-0410-9bdc-e9ce6186880e