Initialize struct flock for AIX with O_LARGEFILE used by Python.

gyp issue 440

Python on AIX is compiled with LARGEFILE support.  gyp flock_tool must
use the appropriate stucture member definitions to properly initialize
the structure.

BUG=
Review URL: https://codereview.chromium.org/738943004/
Patch from David Edelson <dje.gcc@gmail.com>!


git-svn-id: http://gyp.googlecode.com/svn/trunk@2008 78cadc50-ecff-11dd-a971-7dbc132099af