[dwm] dwm-1.1 large numbers of clients diff (includes xinerama)

Hi, attatched is a patch against dwm-1.1 that I use for large numbers of clients (one of my machines is a
two monitor xinerama setup). It makes the numbers of and types of columns fully dynamic, in particular
allowing more than two columns which is very useful for the widescreen display.

I also finally got irritated enough to figure out how to set widths so that with a two monitor setup
columns don't get placed across the monitor split. This is configured via a #define in config.h
so anyone interested can use the same basic codebase on both xinerama and normal setups. One
disadvantage is that I've temporarily removed the "wrap around so zoomed column is towards
middle of display" whilst I figure out a nice way to do; it borders on irritating to have the main
column you're working on always on the left.

As before, very brief documentation is in file called patchDoc.txt that gets created in main dir.

Hi, Anselm: both tag(Arg *arg) and toggletag(Arg *arg) both end with a common section
that I've made into a function in this patch (although I didn't change either tag or toggletag
to minimise churn):

void
processmodifiedtagging(void)
{
        settitle(sel);
        if(!isvisible(sel))
                arrange(NULL);
        else
                drawstatus();
}

This deals with drawing/layout updates when some other logic has changed the tags.
It would be helpful for at least my patches if this (maybe renamed) was in mainstream
dwm. Dunno if it actually reduces lines of code purely wrt mainstream dwm though.

cheers, dave tweed.