Use pkgconfig for libssl.
Use pkgconfig for libssl.

Taken from the Gentoo portage. Either they hadn't bothered to send me
the patch, or I had dropped it.

Signed-off-by: David Woodhouse <b460d66aaf00c296a3db1c1d9eeafc081d5f7d70@intel.com>

don-johnny/openconnect,cernekee/openconnect,certik/openconnect,mtmiller/openconnect,nmav/openconnect-mine,mdutton3/OpenConnect,sihde/openconnect,certik/openconnect,neshema/openconnect,mtmiller/openconnect,chadcatlett/openconnect,matlockx/openconnect,matlockx/openconnect,mtmiller/openconnect,liiir1985/openconnect,matlockx/openconnect,liiir1985/openconnect,don-johnny/openconnect,lins05/openconnect,chadcatlett/openconnect,atyndall/openconnect,liiir1985/openconnect,brandt/openconnect,mtmiller/openconnect,lins05/openconnect,chadcatlett/openconnect,cernekee/openconnect,certik/openconnect,mveplus/openconnect-client,mveplus/openconnect-client,mveplus/openconnect-client,brandt/openconnect,cernekee/openconnect,nmav/openconnect-mine,mveplus/openconnect-client,neshema/openconnect,neshema/openconnect,atyndall/openconnect,matlockx/openconnect,atyndall/openconnect,cernekee/openconnect,atyndall/openconnect,don-johnny/openconnect,lins05/openconnect,brandt/openconnect,lins05/openconnect,mdutton3/OpenConnect,sihde/openconnect,nmav/openconnect-mine,chadcatlett/openconnect,sihde/openconnect,liiir1985/openconnect,neshema/openconnect,don-johnny/openconnect,nmav/openconnect-mine,mdutton3/OpenConnect,brandt/openconnect