[9fans] Alpha compiler chokes on webfs/io.c; various fixes.

[Dan Cross <cross@math.psu.edu>]

Hey Folks,
   Just for the hell of it, last night I decided to try building Plan
9 for a bunch of different architectures.  I encounted a few problems,
and fixed what I could (and what I had time for).  Some diff's (in the
ed-script format, perhaps this'll be easier to apply) follow.
   First, some directories need to be created: /^(power arm)^/bin/ip/httpd
and /^(power arm)^/bin/usb are missing from the distribution.
   Second, the alpha build choked on building io.c in /sys/src/cmd/webfs.
A diff to fix it follows:

term% diff -e /n/sources/plan9/sys/src/cmd/webfs/io.c io.c
52,56c
	addr = va_arg(*arg, char*);
	local = va_arg(*arg, char*);
	dir = va_arg(*arg, char*);
	cfdp = va_arg(*arg, int*);
	usetls = va_arg(*arg, int);
.
term%

Note the *'s before `arg' in the macro call.
   Next, the MIPS compiler (actually, assembler) chokes on the stuff
in /sys/src/libmp/mips, but my MIPS book is literally buried under a
bunch of stuff right now, so I didn't track that down, but perhaps
someone is more familiar with it and knows what's up.
   When building kernels, the mtx build failed due to things missing
during the link stage.  A diff:

term% diff -e /n/sources/plan9/sys/src/9/mtx/mkfile mkfile
21a
	nulledf.$O\
.
17a
	devrealtime.$O\
.
term%

And similarly, the alphapc mkfile needed an addition:

term% diff -e /n/sources/plan9/sys/src/9/alphapc/mkfile mkfile
17a
	devrealtime.$O\
.
term%

That's basically it.  I'm not sure anyone really cares, since alpha's
probably aren't used much anymore, and not a lot of people have mtx's,
but I thought I'd send along the diff's anyway.

	- Dan C.