Move definitions of struct krb5_rc_st, struct _krb5_rc_ops, krb5_rc_ops, and

Move definitions of struct krb5_rc_st, struct _krb5_rc_ops, krb5_rc_ops, and
declarations of krb5_rc_register_type, krb5_rc_dfl_ops from k5-int.h to
rc-int.h.  Include rc-int.h in the krb5/rcache files that need it.

git-svn-id: svn://anonsvn.mit.edu/krb5/trunk@16386 dc483132-0cff-0310-8789-dd5450dbe970