The actual p4 command is open-source software released under the
2-clause BSD license, so we can build it here (for pretty much every
architecture we support!) and include it in the cache.
This change removes the server-side commands from this package, but they
are now available as part of a separate p4d package instead. (The server
package remains unfree.)
As an added bonus, we can also include the libraries and headers for the
C/C++ API, which will allow us to package any software that uses
Perforce as a library in the future.
