Showing warning instead of failing when cached opam file doesn't parse
Implemented the opam 'available' field, superseding 'os' and 'ocaml-version' fields
(does not compile, needs some declarations moved within OpamState, postponed to the
next patch for making merge easier)
Closes #664
Fixed OpamState declaration order
make libinstall should be idempotent
Change OpamArg.repository_address to OpamArg.address and add OpamArg.dirname
Fix the description of 'opam list'
having local archive/dir in url files is allowed
Updated documentation for the 'available:' opam field
Add the url to Not_available
Specialize the address type.

This is now string * string option, where the first component is always the full path and the second component the optional tags (for VCS backends)
Merge branch 'fix-664' of git://github.com/AltGr/opam into AltGr-fix-664

Conflicts:
	src/client/opamState.ml