add flags in gssapi_context_flags

lib/gssapi/mech/doxygen.c

@@ -62,6 +62,23 @@
  *  return status:
  *  - support conf
  *  - support int
+ *
+ * @subsection gssapi_context_flags Context creation flags
+ *
+ * - GSS_C_DELEG_FLAG
+ * - GSS_C_MUTUAL_FLAG
+ * - GSS_C_REPLAY_FLAG
+ * - GSS_C_SEQUENCE_FLAG
+ * - GSS_C_CONF_FLAG
+ * - GSS_C_INTEG_FLAG
+ * - GSS_C_ANON_FLAG
+ * - GSS_C_PROT_READY_FLAG
+ * - GSS_C_TRANS_FLAG
+ * - GSS_C_DCE_STYLE
+ * - GSS_C_IDENTIFY_FLAG
+ * - GSS_C_EXTENDED_ERROR_FLAG
+ * - GSS_C_DELEG_POLICY_FLAG
+
  *
  * @subsection gssapi_services_permessage Per-message services
  *