Fix building of the MockHTTPinC library. We magically inherited the
OpenSSL include paths from apr-util, so everything breaks down if
apr-util doesn't support apr-crypto.

* test/MockHTTPinC/CMakeLists.txt
  (mockhttpinc): Remove target_include_directories. Instead, use the same
   target_link_libraries as the Serf static lib. This exposes the OpenSSL
   include paths directly from the configured target instead of hoping that
   apr-util was build with crypto support.


git-svn-id: https://svn.apache.org/repos/asf/serf/trunk@1927264 13f79535-47bb-0310-9956-ffa450edef68