Add default path to server pipe (cmake build + unix)

Add default path to server pipe (cmake build + unix)

Actually the change is affecting only builds if
1.) Using cmake build
2.) on unix

To use it on
  cygwin: one has to patch development/cygwin/lyxrc.dist.in
  MacOSX:     -//-         development/MacOSX/lyxrc.dist.in

We need also a Windows-version

Also the compilation with automake lacks the handling of development/unix/lyxrc.dist.in