Update libcap to upstream release 2.25
Since the libattr thing was dropped upstream in [1] it is also removed here.
Then, to overcome an issue in cross-compiling [2], set the Make parameter
according to [3].

Take maintainership of this package.

Signed-off-by: Paul Wassi <p.wassi@gmx.at>

[1]:
http://git.kernel.org/cgit/linux/kernel/git/morgan/libcap.git/commit/?id=85f38a573fc47472ab792e813b6f6b6f0b1df112

[2]:
libcap: progs/Makefile:30 executes the cross-compiled binary on the host

[3]:
libcap: Make.Rules: comment from lines 74-81

Remove hardcoded URL and use alias instead.

Signed-off-by: Daniel Engberg <daniel.engberg.lists@pyret.net>