Let's add variant descriptions

[Ryan Schmidt]

How hard would it be to let variants have descriptions? I think the  
time has come for that feature to be implemented. Sometimes the  
single word or abbreviation comprising the variant name just really  
isn't enough information for the user to fully understand what the  
variant does. I have been trying to add descriptions to my ports'  
variants, in the comments in the portfile, but I would like to be  
able to display these to the user.

I see two necessary steps:


1) Allow some (optional!) syntax within the variant to specify a  
description, like

variant macplus {
	description Emulate a Macintosh Plus with 4 MB RAM and 6 drives
	...
}

or

variant macplus {
	variant_description Emulate a Macintosh Plus with 4 MB RAM and 6 drives
	...
}


2) Modify the display of "port info" to show the variant description,  
like


$ port info minivmac
minivmac 2.8.2, Revision 1, emulators/minivmac
http://minivmac.sourceforge.net/

Mini vMac is a Macintosh emulator. It emulates the earliest Macs,  
from the original Mac 128K (built 1984-85) to the Mac SE (1987-1990).  
The default is to emulate a Mac Plus (1986-1990); this is also the  
best-tested and therefore recommended emulation. To use Mini vMac,  
you need a ROM file from the type of machine you're emulating. Mac  
ROMs are copyrighted by Apple, so you must extract the ROM from a  
real physical Mac that you own. Use the CopyROM program for this,  
which you can download from the Mini vMac web site (More > Extras).

Variants:
	universal: Build a universal binary
	mac128k: Emulate a Macintosh with 128K RAM and 2 drives
	mac512k: Emulate a Macintosh 512K with 512K RAM and 2 drives
	mac512ke: Emulate a Macintosh 512Ke with 512K RAM and 6 drives
	macplus: Emulate a Macintosh Plus with 4 MB RAM and 6 drives
	macse: Emulate a Macintosh SE with 4 MB RAM and 6 drives

Maintainers: ryandesign at macports.org


Variants that have no description (i.e. all variants currently) would  
show up just like that, but with just the variant name and no colon  
afterward:


Variants:
	universal
	mac128k
	etc.


Note that I think the automatic platform variants like macosx and  
darwin_8 should not appear at all in port info.


Comments?