Hardcode value of GSS_C_DELEG_POLICY_FLAG

This value is fortunately specified by RFC 5896.  Truly ancient Kerberos
implementations, such as the Heimdal in base on FreeBSD at the time of
writing, will not provide this flag.  However, since unknown flags will
be ignored, it's fine to just provide it anyway.

Resolves: #228

Signed-off-by: Robbie Harwood <rharwood@redhat.com>

gssapi/raw/types.pyx

@@ -56,7 +56,11 @@ class RequirementFlag(IntEnum, metaclass=ExtendableEnum):
     anonymity = GSS_C_ANON_FLAG
     protection_ready = GSS_C_PROT_READY_FLAG
     transferable = GSS_C_TRANS_FLAG
-    ok_as_delegate = GSS_C_DELEG_POLICY_FLAG
+
+    # GSS_C_DELEG_POLICY_FLAG.  cython can't do compile-time detection of
+    # this, so take the value from RFC 5896.  Implementations that don't
+    # support it will ignore it.
+    ok_as_delegate = 32768
 
 
 class AddressType(IntEnum, metaclass=ExtendableEnum):