Log Message:
Apache Serf 1.3.9:
  serf is now Apache Serf; apply header changes
  Fix issue 151: SCons build broken when only one library in ENVPATH
  Fix issue 153: avoid SSPI handle leak
  Fix issue 167: Explicitly use the ANSI version of SSPI
  Fix issue 170: Allow building with Microsoft Visual Studio 2015
  Fix build of 'check' target when using VPATH-style builds
    (builddir != srcdir).
  Resolve a bucket (aka "memory") leak when a request bucket is
    destroyed before it is morphed into an aggregate bucket
  Reset state variables when resetting connection
  Fix types of passed, but unused batons
  Fix some usages of the openssl BIO api
  Improve handling of bad data in the response state line.
  Resolve several compiler issues with less common compilers
  Support more overrides via SCons arguments
  Adapt to OpenSSL 1.1.x api