Make the version as part of package name of

Make the version as part of package name of
cmake build be configurable.
Use -DLYX_LOCALVERSIONING=ON (default = OFF)
The package name will then be
	lyx-2.1.0-xxxxgit-yyyy.zzz
where xxxx == version number (similar to svn)
      yyyy == your OS (e.g. Linux)
      zzz  == package extension (e.g. deb, rpm, tar.gz etc)

otherwise the string '-xxxxgit' will not be used.