patch file name convention changed

[Thomas Klausner <wiz%NetBSD.org@localhost>]

Per the discussion on tech-pkg last June, I've now updated the pkgsrc
guide to mention that patch file names should contain the file name
path of the to-be-patched file.

I've also improved the pkgdiff tools. Here's the commit message:

--- quote ---
Smarter pkgdiff, doesn't create chunks that are added automatically by
the pkgsrc infrastructure (configure:exit instead of regenerate,
Makefile: localedir).

mkpatches: patch file names now contain the path to the file and its
name per discussion on tech-pkg June 2010.  Also, the files are
created directly in the patches/ directory; backups are saved as
patches/patch-foo.orig.

patchdiff: now compares patches/patch-foo with patches/patch-foo.orig;
if they only differ in non-essential parts, patchdiff reinstates the
original patch to keep commits less noisy.
--- end quote ---

The old patch file name convention is still mentioned in the pkgsrc
guide.

Cheers,
 Thomas