FAQ and Wiki page about -Wimplicit-function-declaration warning, review welcomed

[Jim DeLaHunt]

Hello, MacPorts developers:

I was working on a Portfile, and came across the ever-popular "Warning: 
Configuration logfiles contain indications of 
-Wimplicit-function-declaration; check that features were not 
accidentally disabled". After a little searching, I could not find good 
instructions on what it meant to me and what I should do. After a bit 
more searching, I found useful posts to macports-dev and macports-user 
from last year.

I took what I learned, and wrote the wiki entries I wished I had found 
with just a little searching. I would welcome your review, and 
improvements. Go right ahead and edit the wiki entries if you want.

I added an FAQ:
Why am I getting a message, "Warning… indications of 
-Wimplicit-function-declaration"?
<https://trac.macports.org/wiki/FAQ#WhyamIgettingamessageWarningindicationsof-Wimplicit-function-declaration>

This FAQ is intended to be easy to find, and give a user who sees the 
warning (without having followed macports-dev and macports-user in 
detail for a year) some confidence that this is a known phenomenon, and 
some simple instructions on what to do about it.

I added a wiki page. It is intended to be sufficient for users in the 
first section, and sufficient for portfile developers in the remaining 
sections. It also shows up nicely in wiki search results for the text of 
the warning message.

WimplicitFunctionDeclaration 
<https://trac.macports.org/wiki/WimplicitFunctionDeclaration>

WimplicitFunctionDeclaration is wiki shorthand for a particular warning 
message, "Warning: Configuration logfiles contain indications of 
-Wimplicit-function-declaration; check that features were not 
accidentally disabled", which MacPorts sometimes displays when 
configuring a port. This page explains what you as a MacPorts user 
should understand about this message, and what helpful steps you can 
take. It also explains to port maintainers, and the adventurer who wants 
to diagnose the problem behind the warning, the reason why the message 
appears, and how to pursue the problem to the upstream developers.

Page structure:
WimplicitFunctionDeclaration
         The warning
         Respond by filing MacPorts ticket(s)
         What it means
         Diagnosis
         Respond by filing upstream bug reports
         See also
             Macports-users email threads
             GNU Automake tools

Having written all that, I hope that I have equipped other novice 
Portfile developers to be prepared to turn these warnings into upstream 
bug fixes for their ports. I will now work on upstream bug reports for 
my ports.

I will revisit the WimplicitFunctionDeclaration page from time to time 
to do copy editing and to add new findings.

Best regards,
     —Jim DeLaHunt, Vancouver, Canada