The hdb_method functions cannot be KRB5_LIB_CALL as lib/hdb is not
lib/krb5. KRB5_LIB_CALL will be inconsistently defined.
This inconsistency resulted in crashes of test_hdbplugin on 32-bit
Windows.
Change-Id: I4cf8d3ef76f31a3cae923df234a19610d956e7ee