Haiku OS Support

As a part of Google Summer of Code 2014, I was working on porting libusb to Haiku. Finalising the work, I am creating this pull request, to merge my changes into libusb. Please review.
Thanks for your time.

Akshay Jaggi

[1] Haiku OS (http://haiku-os.org)
[2] Link to Proposal (http://www.google-melange.com/gsoc/proposal/public/google/gsoc2014/akshay1994/5629499534213120)