Add thread api

 On branch para
 Changes committed:
    modified:   lib/os.h
    modified:   lib/os_base.c
    modified:   lib/os_base.h
    modified:   lib/os_thread.c
    modified:   lib/os_thread.h
    modified:   lib/os_time.h
    modified:   lib/setup.c
    new file:   lib/vm.c
    new file:   lib/vm.h
Commits forgotten file in the preceding commit

 On branch para
 Changes committed:
    modified:   include/gambit.h.in
Merge ../gambit.old into para

 On branch para
 Changes to be committed:

	modified:   include/gambit.h.in
	modified:   lib/makefile.in
	modified:   lib/os.h
	modified:   lib/os_base.c
	modified:   lib/os_base.h
	modified:   lib/os_thread.c
	modified:   lib/os_thread.h
	modified:   lib/os_time.h
	modified:   lib/setup.c
	new file:   lib/vm.c
	new file:   lib/vm.h