Add a mechanism for growing the stacks on demand by adding new segments

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Add a mechanism for growing the stacks on demand by adding new segments
to them. You can ask for the new mechanism via a new grade component, stseg
(short for "stack segments").

The mechanism works by adding a test to each increment of a stack pointer (sp
or maxfr). If the test indicates that we are about to run out of stack, we
allocate a new stack segment, allocate a placeholder frame on the new segment,
and then allocate the frame we wanted in the first place on top of the
placeholder. We also override succip to make it point code that will (1)
release the new segment when the newly created stack frame returns, and then
(2) go to the place indicated by the original, overridden succip.

For leaf procedures on the det stack, we optimize away the check of the stack
pointer. We can do this because we reserve some space on each stack for the
use of such stack frames.

My intention is that doc/user_guide.texi and NEWS will be updated once we have
used the feature ourselves for a while and it seems to be stable.

runtime/mercury_grade.h:
	Add the new grade component.

runtime/mercury_conf_param.h:
	Document the new grade component, and the option used to debug stack
	segments.

runtime/mercury_context.[ch]:
	Add new fields to contexts to hold the list of previous segments of the
	det and nondet stacks.

runtime/mercury_memory_zones.[ch]:
	Include a threshold in all zones, for use in stack segments.
	Set it when a zone is allocated.

	Restore the previous #ifdef'd out function MR_unget_zone, for use
	when freeing stack segments execution has fallen out of.

runtime/mercury_debug.[ch]:
	When printing the offsets of pointers into the det and nondet stacks,
	print the number of the segment the pointer points into (unless it is
	the first, in which case we suppress this in the interest of brevity
	and simplicity).

	Make all the functions in this module take a FILE * as an input
	argument; don't print to stdout by default.

runtime/mercury_stacks.[ch]:
	Modify the macros that allocate stack frames to invoke the code for
	adding new stack segments when we are about to run out of stack.

	Standardize on "nondet" over "nond" as the abbreviation referring to
	the nondet stack.

	Conform to the changes in mercury_debug.c.

runtime/mercury_stack_trace.c:
	When traversing the stack, step over the placeholder stack frames
	at the bottoms of stack segments.

	Conform to the changes in mercury_debug.c.

runtime/mercury_wrapper.[ch]:
	Make the default stack size small in grades that support stack
	segments.

	Standardize on "nondet" over "nond" as the abbreviation referring to
	the nondet stack.

	Conform to the changes in mercury_debug.c.

runtime/mercury_memory.c:
	Standardize on "nondet" over "nond" as the abbreviation referring to
	the nondet stack.

runtime/mercury_engine.[ch]:
runtime/mercury_overflow.h:
	Standardize on "nondet" over "nond" as the abbreviation referring to
	the nondet stack.

	Convert these files to four-space indentation.

runtime/mercury_minimal_model.c:
trace/mercury_trace.c:
trace/mercury_trace_util.c:
	Conform to the changes in mercury_debug.c.

compiler/options.m:
	Add the new grade option for stack segments.

compiler/compile_target_code.m:
compiler/handle_options.m:
	Add the new grade component, and handle its exclusions with other grade
	components and optimizations.

compiler/llds.m:
	Extend the incr_sp instruction to record whether the stack frame
	is for a leaf procedure.

compiler/llds_out.m:
	Output the extended incr_sp instruction.

compiler/proc_gen.m:
	Fill in the extra slot in incr_sp instructions.

compiler/goal_util.m:
	Provide a predicate for testing whether a procedure body is a leaf.

compiler/delay_slot.m:
compiler/dupelim.m:
compiler/dupproc.m:
compiler/exprn_aux.m:
compiler/frameopt.m:
compiler/global_data.m:
compiler/jumpopt.m:
compiler/middle_rec.m:
compiler/opt_debug.m:
compiler/opt_util.m:
compiler/peephole.m:
compiler/reassign.m:
compiler/use_local_vars.m:
	Conform to the change in llds.m.

scripts/canonicate_grade.sh-subr:
scripts/init_grade_options.sh-subr:
scripts/parse_grade_options.sh-subr:
scripts/final_grade_options.sh-subr:
scripts/mgnuc.in:
	Handle the new grade component.

	Convert parse_grade_options.sh-subr to four-space indentation.

Mmake.workspace:
	Fix an old bug that prevented bootcheck from working in the new grade:
	when computing the gc grade, use the workspace's version of ml (which
	in this case understands the new grade components), rather than the
	installed ml (which does not).

	(This was a devil to track down, because neither make --debug nor
	strace on make revealed how the installed ml was being invoked,
	and there was no explicit invocation in the Makefile either; the error
	message appeared to come out of thin air just before the completion
	of the stage 2 library. It turned out the invocation happened
	implicitly, as a result of expanding a make variable.)

scripts/final_grade_options.sh-subr

@@ -1,5 +1,5 @@
 #---------------------------------------------------------------------------#
-# Copyright (C) 1998-2002, 2004-2005 The University of Melbourne.
+# Copyright (C) 1998-2002, 2004-2006 The University of Melbourne.
 # This file may only be copied under the terms of the GNU General
 # Public License - see the file COPYING in the Mercury distribution.
 #---------------------------------------------------------------------------#
@@ -40,6 +40,15 @@ case $use_trail,$use_minimal_model in true,true)
 	exit 1 ;;
 esac
 
+#
+# .exts grade is not compatible with .stseg
+#	(they are alternative ways of doing the same thing)
+#
+case $extend_stacks,$stack_segments in true,true)
+	echo "--extend-stacks-when-needed and --stack-segments are not compatible" 1>&2
+	exit 1 ;;
+esac
+
 #
 # .debug grade (but not .decldebug) implies --use-trail in the absence of .*mm*
 #	(see comment in compiler/handle_options.m for rationale)