Implement experimental DNSSEC DANE support

This patch adds experimental support for the DNSSEC DANE verification
protocol using the libval library from the DNSSEC-Tools package.

Thanks to Thomas Steen Ramussen for creating a test setup and suggesting
the idea of experimenting with DANE support in Irssi :-)

git-svn-id: http://svn.irssi.org/repos/irssi@5218 dbcabf3a-b0e7-0310-adc4-f8d773084564
Pass SERVER_REC directly to net_connect_ip_ssl

This patch refactors how we are passing connection information for SSL
connections. This will allow us to emit signals with a SERVER_REC as
parameter during SSL handshake.

git-svn-id: http://svn.irssi.org/repos/irssi@5219 dbcabf3a-b0e7-0310-adc4-f8d773084564
Add TLSA related signals

This patch adds 3 new signals:

  * tlsa avalable: emitted if TLSA is available for a given domain.
  * tlsa verification success: emitted if the TLSA check was successful.
  * tlsa verification failed: emitted if the TLSA check was unsuccessful.

git-svn-id: http://svn.irssi.org/repos/irssi@5220 dbcabf3a-b0e7-0310-adc4-f8d773084564
Fix build for FreeBSD

git-svn-id: http://svn.irssi.org/repos/irssi@5221 dbcabf3a-b0e7-0310-adc4-f8d773084564
Check for OpenSSL support for --enable-dane

It doesn't make any sense to build Irssi without SSL support, but with
DANE support. This patch adds an extra check in the configure script
that will make the script bail out if someone tries to build Irssi with
DANE support, but without OpenSSL support.

git-svn-id: http://svn.irssi.org/repos/irssi@5222 dbcabf3a-b0e7-0310-adc4-f8d773084564