Allow external hcrypto

Put the configure checks into a separate file in src/cf, following
the same general structure as the roken checks.

Allow explicitly requesting the internal version, or checking
what's in the default paths, or providing a specific hcrypto root
or lib/include dirs for Debian compatibility.

We must still always compile libafshcrypto_lwp.a for use by LWP
binaries, from the bundled sources, but other binaries will use
the system version.

The hcrypto headers have an unfortunately large number of dependencies,
including depending on being able to find each other by including
<hcrypto/foo.h> paths.  As such we must pass both the user-supplied
directory and $dir/hcrypto to the preprocessor in order for things
to work, and we also may need to revisit the includes used in the
configure check for use on non-linux systems due to the dependencies
on system headers.

Change-Id: Idcba1418a19a7b562335524c911d69dc84268177
Reviewed-on: http://gerrit.openafs.org/11481
Reviewed-by: Benjamin Kaduk <kaduk@mit.edu>
Reviewed-by: D Brashear <shadow@your-file-system.com>
Tested-by: D Brashear <shadow@your-file-system.com>
Build hcrypto with libtool

Or rather, with lwptool, since we need a LWP version as well as
the various pthreaded versions.

The previous version was the initial version, 1.1, but since we're
switching to libtool, bump the version to 2.0 just to be safe.

Libtool abstracts away the extra logic that had previously been needed
to build different copies of rand-fortuna for the pthreaded and LWP
libraries.

As for roken, we must install both shared and static libraries
to $(TOP_LIBDIR) for unity of consumption, but remove the libtool
archive after instllation.

Change-Id: Ibc530a1fa4baa7a38b44eb3e0719e1905a6fe269
Reviewed-on: http://gerrit.openafs.org/11482
Reviewed-by: Benjamin Kaduk <kaduk@mit.edu>
Reviewed-by: D Brashear <shadow@your-file-system.com>
Tested-by: D Brashear <shadow@your-file-system.com>