Use libvpx's obj_int_extract and unpack_lib_posix to generate offset header file.

This patch removes generate_asm_header.gypi and uses libvpx's obj_int_extract and
unpack_lib_posix to generate offset header files.

It make the simliar feature's implementation consistent.

R=andrew@webrtc.org, fischman@webrtc.org, fischman@chromium.org
BUG=334447

Committed: https://code.google.com/p/webrtc/source/detail?r=5517

Review URL: https://webrtc-codereview.appspot.com/7769006

git-svn-id: http://webrtc.googlecode.com/svn/trunk/webrtc@5524 4adac7df-926f-26a2-2b94-8c16560cd09d
7 files changed