[test suite] minor variable conversion to 'our' vars
convert HMAC functions to static where possible
[test suite] derive HMAC digest type from client display context output
added HMAC SHA384 and SHA512 support, bug fix to allow shorter HMAC key lengths than associated digest block size
SPA with HMAC SHA256 and SHA384 now works

This is a fairly significant commit that lays the groundwork for getting
selectable HMAC modes working for both the client and server.  One libfko API
change was required so that the hmac_type is passed into fko_new_with_data().
This allows the server to set the hmac_type via access.conf stanzas.  The
effort in this commit will be extended to allow HMAC MD5, SHA1, and SHA512
also function properly.
Merge branch 'hmac_support' of github.com:mrash/fwknop into hmac_support

Conflicts:
	client/fwknop.c
	lib/fko_hmac.c