Make all linux ptrace dumper tests use a subprocess
Patch by Mike Hommey <mh@glandium.org>, R=ted at https://breakpad.appspot.com/550002/

git-svn-id: http://google-breakpad.googlecode.com/svn/trunk@1190 4c0a9323-5329-0410-9bdc-e9ce6186880e
add interface for WriteMinidump which allows the caller to supply file handles instead of paths where the minidumps should be written.

BUG=N/A
TEST=N/A
R=ivan.penkov@gmail.com, mark@chromium.org

Review URL: https://breakpad.appspot.com/602002

git-svn-id: http://google-breakpad.googlecode.com/svn/trunk@1191 4c0a9323-5329-0410-9bdc-e9ce6186880e