gss-server.c: Re-added code to test import and export security

gss-server.c: Re-added code to test import and export security
	context.  Yes, yes, I know this isn't the best place to have this
	test, but DO NOT REMOVE THIS TEST UNTIL WE HAVE IT CODED ELSEWHERE.
	Better slightly ugly sample server code than untested (and broken)
	library code....  Add code to print out the mechanism OID used by
	accept_sec_context.

gss-client.c: Add code to allow user to specify the mechanism
	OID that gss-client should use.

git-svn-id: svn://anonsvn.mit.edu/krb5/trunk@9230 dc483132-0cff-0310-8789-dd5450dbe970