[DRAFT] ports contributor's guide

[Mark Linimon]

One of the other ideas I have for this document is to emphasize
that one of our most pressing needs right now is to get the
ports tree in good shape on 5.x.  Many of these problems are
due to a few underlying changes in gcc, such as 'no more
varargs.h, no more multiline constants unless you say that's
really what you want, no more assuming "standard namespace"
in c++ code', and so forth.  The bento pages are are a really
good way to see how common these kinds of bugs are.

Really, by the time we branch a 5-STABLE, it would be very
desireable to get 100 or 200 more ports either working with
gcc3.3, or declared obsolete if they're abandonware.

mcl