Split of architecture-dependent and -independent functions for i386,

mainly in the kernel and headers. This split based on work by
Ingmar Alting <iaalting@cs.vu.nl> done for his Minix PowerPC architecture
port.

 . kernel does not program the interrupt controller directly, do any
   other architecture-dependent operations, or contain assembly any more,
   but uses architecture-dependent functions in arch/$(ARCH)/.
 . architecture-dependent constants and types defined in arch/$(ARCH)/include.
 . <ibm/portio.h> moved to <minix/portio.h>, as they have become, for now,
   architecture-independent functions.
 . int86, sdevio, readbios, and iopenable are now i386-specific kernel calls
   and live in arch/i386/do_* now.
 . i386 arch now supports even less 86 code; e.g. mpx86.s and klib86.s have
   gone, and 'machine.protected' is gone (and always taken to be 1 in i386).
   If 86 support is to return, it should be a new architecture.
 . prototypes for the architecture-dependent functions defined in
   kernel/arch/$(ARCH)/*.c but used in kernel/ are in kernel/proto.h
 . /etc/make.conf included in makefiles and shell scripts that need to
   know the building architecture; it defines ARCH=<arch>, currently only
   i386.
 . some basic per-architecture build support outside of the kernel (lib)
 . in clock.c, only dequeue a process if it was ready
 . fixes for new include files

files deleted:
 . mpx/klib.s - only for choosing between mpx/klib86 and -386
 . klib86.s - only for 86

i386-specific files files moved (or arch-dependent stuff moved) to arch/i386/:
 . mpx386.s (entry point)
 . klib386.s
 . sconst.h
 . exception.c
 . protect.c
 . protect.h
 . i8269.c

kernel/system/do_fork.c

@@ -8,9 +8,6 @@
 
 #include "../system.h"
 #include <signal.h>
-#if (CHIP == INTEL)
-#include "../protect.h"
-#endif
 
 #include <minix/endpoint.h>
 
@@ -23,7 +20,7 @@ PUBLIC int do_fork(m_ptr)
 register message *m_ptr;	/* pointer to request message */
 {
 /* Handle sys_fork().  PR_ENDPT has forked.  The child is PR_SLOT. */
-#if (CHIP == INTEL)
+#if (_MINIX_CHIP == _CHIP_INTEL)
   reg_t old_ldt_sel;
 #endif
   register struct proc *rpc;		/* child process pointer */
@@ -42,10 +39,10 @@ register message *m_ptr;	/* pointer to request message */
 
   /* Copy parent 'proc' struct to child. And reinitialize some fields. */
   gen = _ENDPOINT_G(rpc->p_endpoint);
-#if (CHIP == INTEL)
-  old_ldt_sel = rpc->p_ldt_sel;		/* backup local descriptors */
+#if (_MINIX_CHIP == _CHIP_INTEL)
+  old_ldt_sel = rpc->p_seg.p_ldt_sel;	/* backup local descriptors */
   *rpc = *rpp;				/* copy 'proc' struct */
-  rpc->p_ldt_sel = old_ldt_sel;		/* restore descriptors */
+  rpc->p_seg.p_ldt_sel = old_ldt_sel;	/* restore descriptors */
 #else
   *rpc = *rpp;				/* copy 'proc' struct */
 #endif