Support more than 63 jobs on MS-Windows

Support more than 63 jobs on MS-Windows

* job.c (start_waiting_job, load_too_high):
* w32/w32os.c (jobserver_setup, jobserver_acquire): Abstracted out
MAXIMUM_WAIT_OBJECTS.  Call process_table_full instead.
* w32/include/sub_proc.h: Update and add prototypes.
* w32/subproc/sub_proc.c (GMAKE_MAXIMUM_WAIT_OBJECTS): New macro.
(process_wait_for_multiple_objects): Drop-in replacement for Windows
API WaitForMultipleOjects.
(process_wait_for_any_private): Replaced MAXIMUM_WAIT_OBJECTS with
GMAKE_MAXIMUM_WAIT_OBJECTS.
(process_table_full): Replacement for process_used_slots.
(process_used_slots): Removed, as no longer needed.
(process_table_usable_size): Returns maximum usable size of process
table.
(process_table_actual_size): Returns actual size of process table.
(process_register): Added assertion.
(process_easy): Abstracted out MAXIMUM_WAIT_OBJECTS.