Long live QLockFile

Locking between processes, implemented with open(O_EXCL) on Unix
and CreateFile(CREATE_NEW) on Windows.

Supports detecting stale lock files and deleting them.
Advisory locking is used to prevent deletion of files that are still in use.

Change-Id: Id00ee2a4e77a29483d869037c7047c59cb909339
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>