New wiki page PortfileRecipes

[Bryan Blackburn]

FYI I've added a new wiki page:

<http://trac.macports.org/wiki/PortfileRecipes>

The basic idea being to list certain otherwise-undocumented best practices
that come up from time to time.  Many techniques may have the basic commands
documented (like reinplace) but some of the common uses aren't, so these
bits tend to come up from time to time on the list.

One important thing I think for this page is to always have examples or
references to actual ports using the given technique (or both) to help with
those new to creating ports.

Obviously some which aren't "failures" in port can be moved to the guide
when cleaned up and whatnot, others should probably have tickets if they
don't already, and the rest probably can become integrated where needed.

Bryan