Test a defined/undefined boolean macro with "#ifdef" rather than "#if", for strict compatibility with its definition, thus avoiding a compiler warning.
Test a defined/undefined boolean macro with "#ifdef" rather than "#if", for
strict compatibility with its definition, thus avoiding a compiler warning.

* subversion/libsvn_subr/simple_providers.c
  (svn_auth_get_windows_simple_provider): Test SVN_HAVE_KEYCHAIN_SERVICES
    with "#ifdef".

jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion