* Add package for libbsd, add variant to expat for libbsd
The recent expat release requires a high quality source of randomness.
CentOS 7 does not seem to have one, but one is available in libbsd.
This commit adds a package for libbsd and adds a variant to expat to
use it (defaults to False).
* Make libbsd default for newer, conflict for older
Make the libbsd variant default to true.
Conflict if you're asking for libbsd and an older version of expat.
This means that in order to install an older version of expat you'll
need to specify `~libbsd`.
* Rework so that 2.2.0 and 2.2.2 work by default
Get rid of the conflicts and use better constraints/tests in the
`depends_on` and the `configure_args` bits.
* Remove +mpi variant from NCO
* Update NCO deps to AutotoolsPackage
* Update the other NetCDF packages to AutotoolsPackage
* ANTLR has a nolink deptype on java, don't worry about csharp
* Remove restrictions from NCO package, fix homepage
* Add version 4.6.3 of NCO
* Missed AutotoolsPackage for NetCDF-CXX4
* NetCDF tests fail when run in parallel
* Remove commented out dependency
* Add documentation dependency
