Merge branch 'maint'

* maint:
  index.py: handle uid/gid == -1 on cygwin
  cmd/memtest: use getrusage() instead of /proc/self/stat.
  cmd/index: catch exception for paths that don't exist.
  Don't use $(wildcard) during 'make install'.
  Don't forget to install _helpers.dll on cygwin.