Add a header file which got missed out in the initial commit.
This header is not required on windows and mac since the types are defined already for those platforms.

TEST=none
BUG=none

Review URL: http://codereview.chromium.org/3142018

git-svn-id: http://src.chromium.org/svn/trunk/deps/third_party/speex@56503 4ff67af0-8c30-449e-8e8b-ad334ec8d88c