Remove internal xen activations functions from the interface
xen: Gnttab.unmap_exn should surely throw an exception, given the suffix

For a well-behaved mirage app the unmap should never fail (because
a page is still in use) because we will manage our mappings carefully.
Merge pull request #38 from djs55/gnttab-unmapexn

Fix a minor mismatch in the Gnttab interface
Add CHANGES entry for gnttab.unmap_exn
Add code to generate documentation
Merge pull request #31 from vbmithr/master

Add code to generate doc
Documented and refactored Console modules of the Xen and UNIX backends
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
Merge pull request #41 from vbmithr/doc

Doc of Io_pages, typos in Gnttab, updated CHANGES
Sync CHANGES with recent changes
bump to 0.9.0
Doc for module Clock (UNIX/Xen)
Documentation for module Time (UNIX/Xen)
Documented module Start_info (Xen)
Added doc for module Env (UNIX/Xen)
[doc] Titles and typos.