BUILD description in the docs

[Egbert Eich]

The BUILD notes contain this paragraph:

Alternatively, if you already have a pristine copy of the X11R6.7.0 6.6.0
source, you can download patches from ftp://ftp.x.org/pub/R6.7.0/fixes/ that
will allow you to convert it to 6.7.0.  Information about which patch files
to download and how to apply them can be found in the "How to get X11R6.7.0"
section of the README for this release.

Do we want to provide diffs against 6.6.0? I'd like suggest to drop this.

Apart from this I saw CVS tags in the tree: xo-6.7_0, xo-6.7-branch.

I don't object to these names however please keep in mind that CVS tags
must not contain '.'. I'll fix it.

Cheers,
	Egbert.