1.0.30.23: adjust OpenBSD address spaces on x86

1.0.30.23: adjust OpenBSD address spaces on x86

 * Patch by Josh Elsasser. He says:

   "The current address space locations for x86 OpenBSD are adequate,
   but could still be better chosen. The only real problem with the
   current addresses is that the default dynamic space size is larger
   than the default data size resource limit, which means that sbcl
   will not run without some tweaking. Attached is a patch to lower
   the dynamic space size, as well as move all spaces to locations
   which I suspect may prove more future-proof against OpenBSD
   changes. The patch also greatly expands the OpenBSD comment. I
   apologize for the verbosity, but the address space layout on
   OpenBSD/i386 is quite complex and I wanted to record the details
   before I forgot (again)."

   Committing untested, as I don't have an OpenBSD system available.