Factor out libidn, libp11-kit and libtspi into OPTIONal library
dependencies, with the CRYWRAP, P11KIT and TPM options respectively, as per
the upstream documentation [1].
Make ZLIB an OPTION because we can, and the choice to customise
compression support in security software (especially lately) may be
very useful for some consumers.
Add CRYWRAP, P11KIT, TPM and ZLIB to OPTIONS_DEFAULT to retain current
default functionality.
[1] http://gnutls.org/manual/html_node/Downloading-and-installing.html
Inspired by: Recent gnutls 2 -> 3 change, fan of minimal dependencies
PR: 192090
Submitted by: koobs
Approved by: maintainer
