src/server.scm (server?): New procedure.

* src/server-type.c (guile_ssh_is_server_p): New procedure.
* src/server-type.h (guile_ssh_is_server_p): Export.
* src/server.scm (server?): Export.
* NEWS: Update.
Merge branch 'master' into tests-implementation

Conflicts:
	ChangeLog
tests/server.scm: Add new TCs.

* tests/server.scm ("server?", "comparison of servers"): New TCs.