Make the serf.def file a proper target in the CMake build, so that it gets
regenerated during the build if any of the public headers change.

* CMakeLists.txt: Use the current source directory everywhere to keep
   references localised for external scripts. Add a custom target for
   generating the serf.def file.

* build/SerfWindowsGenDef.cmake: New script, generates the .def file.
* build/SerfWindowsGenDef.cmake: Make the regular expressions more readable.

git-svn-id: https://svn.apache.org/repos/asf/serf/trunk@1835100 13f79535-47bb-0310-9956-ffa450edef68
3 files changed