Add CHANGES entry for gnttab.unmap_exn
Merge pull request #39 from djs55/gnttab-unmapexn

Add CHANGES entry for gnttab.unmap_exn
Merge pull request #40 from vbmithr/doc

Documented and refactored Console modules of the Xen and UNIX backends
Typos in gnttab.mli
Documentation of module Io_page and improvement of the Io_page.string_blit function.
Updated CHANGES