Add a test to find the number of words needed to represent a

configure.in:
        Add a test to find the number of words needed to represent a
        synchronization term.

boehm_gc/gc.h:
        fix a declaration by replacing the args () with (void).
boehm_gc/solaris_pthreads.c:
        add a missing include
        check the return values of pthread calls.

compiler/*.m:
        Add handling for the new HLDS goal type par_conj.
        Add handling for the four new LLDS instructions:
                init_sync_term
                fork
                join_and_terminate
                join_and_continue

compiler/code_info.m:
        add a new alternative for slot_contents - sync_term.

compiler/handle_options.m:
        add .par as part of the grade

compiler/hlds_goal.m:
        add the new goal type par_conj.

compiler/instmap.m:
        add instmap__unify which takes a list of instmaps
                and abstractly unifies them.
        add unify_instmap_delta which tajes two instmap deltas
                and abstractly unifies them.

compiler/llds.m:
        add the new llds instructions.

compiler/mode_info.m:
        add par_conj as a lock reason.

library/Makefile:
        work around a bug in the solaris version pthread.h

library/benchmarking.m:
        reference the stack zones from the engine structure
        rather than from global variables.

library/{nc,sp}_builtin.nl:
        add an op declaration for &.

library/std_util.m:
        change references to global variables to references inside
        the engine structure.

runtime/Mmakefile:
        add mercury_thread.{c,h}
        add THREADLIBS to the libraries

runtime/*.{c,h}
        Remove some old junk from the previous processes/shrd-mem
        changes that found their way into the repository.
        Add MR_ prefixes to lots of names.

runtime/mercury_context.c:
        Add init_thread_stuff for creating and initializing a
        context structure for the current thread.

runtime/mercury_context.h:
        add a field to the mercury context which stores the thread id
        of the thread where this context originated.
        add various macros for implementing the new llds instructions.

runtime/mercury_engine.c:
        initialize the engine structure, rather than a bunch of globals.

runtime/mercury_engine.h:
        declare the mercury_engine structure.

runtime/mercury_regorder.h:
        if MR_THREAD_SAFE, and there is at least one global register
        then use mr0 as a pointer to the mercury engine structure.

scripts/init_grade_options.sh-subr
        add thread_safe

scripts/mgnuc.in
        add THREAD_OPTS

scripts/ml.in:
        add THREAD_LIBS

scripts/init_grade_options.sh-subr

@@ -25,6 +25,7 @@ args_method=compact
 stack_trace=false
 require_tracing=false
 low_level_debug=false
+thread_safe=false
 
 case $# in
 	0) set - "--grade $DEFAULT_GRADE" ;;