Don't make krb5_ccache point into krb5_context allocated memory

Don't make a copy of the krb5_cc_ops into krb5_context and hand that
out to callers of the api, this way its possible to free a krb5_context
w/o invalidating all krb5_ccaches that was allocated using that krb5_context
(also, it saves memory)

lib/krb5/krb5_locl.h

@@ -234,7 +234,7 @@ typedef struct krb5_context_data {
     krb5_config_section *cf;
     struct et_list *et_list;
     struct krb5_log_facility *warn_dest;
-    krb5_cc_ops *cc_ops;
+    const krb5_cc_ops **cc_ops;
     int num_cc_ops;
     const char *http_proxy;
     const char *time_fmt;