gss-server.c (sign_server): Do better import/export security checking.

gss-server.c (sign_server): Do better import/export security checking.
	If the received message to be signed is not printable (at least the
	first two characters are not), display the message in hex.  Print the
	hex values of the incoming and outcoming packets, for your
	information.

gss-misc.c (print_token, display_buffer): Two new tokens for
	displaying GSSAPI buffers, either has hex or as a printable string.

gss-client.c (call_server): Add option to support reading in the
	message to be signed from a file.

git-svn-id: svn://anonsvn.mit.edu/krb5/trunk@7583 dc483132-0cff-0310-8789-dd5450dbe970