--enable-maintainer-mode for toplevel

[Ben Elliston]

>>>>> "Alexandre" == Alexandre Oliva <aoliva@redhat.com> writes:

  Alexandre> After being bitten by inappropriate timestamps in the
  Alexandre> top-level configure file one too many times (and not
  Alexandre> willing to recommend the use of gcc's contrib/gcc_update
  Alexandre> for the src tree), I went ahead and disabled the
  Alexandre> timestamp dependencies of the top-level Makefile.in and
  Alexandre> configure unless --enable-maintainer-mode (borrowed from
  Alexandre> automake) is used.  I'm checking this in mainline.

Thanks for fixing this, Alex.  It's been a pain in the neck.

Ben