Linux: change gyp and add a shim header to build with system speex.

This will be useful for Linux distributions shipping Chromium.
The default setting is still to build with the bundled speex library.

More changes will be required (in src). This is the part in deps.

BUG=68524
TEST=none
Review URL: http://codereview.chromium.org/5990013

git-svn-id: http://src.chromium.org/svn/trunk/deps/third_party/speex@70427 4ff67af0-8c30-449e-8e8b-ad334ec8d88c
2 files changed