libkcapi: new package

libkcapi: new package

This package provides a userspace library that allows easy use of crypto
interfaces exposed by the kernel.

A git tip is used instead of the last official release, as autotools
support and cross-compilation fixes have been added only very recently.

Signed-off-by: Marcin Nowakowski <marcin.nowakowski@imgtec.com>
Reviewed-by: Rahul Bedarkar <rahul.bedarkar@imgtec.com>
[Thomas:
 - Change sub-option prompt to "build test applications"
 - Be more specific about the license: the library is under BSD-3c only,
   while the programs are under BSD-3c or GPLv2.
 - Explicitly disable programs when BR2_PACKAGE_LIBKCAPI_APPS is not
   enabled.]
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>