PATH environment variable required

[Thad Thompson]

Not sure if this is a bug or a required prerequisite, so I thought I'd
submit it to the list if for nothing else but FYI:

opkg segfaults if there is no exported PATH environment variable. If
you're wondering why on earth anyone would ever NOT have PATH defined,
it seems that ash from Busybox uses a rather sensible default, so it's
quite possible to have a useable system without it. 

The (first) faulting location is in libopkg/opkg_cmd.c:319: 
	ctx->oldpath = strdup (getenv ("PATH"));

In the meantime, I think I'll take the weenie way out and just define
it. 

- Thad