Support concurrency in Emacs Lisp

Merge branch 'test-concurrency'

* src/thread.c:
* src/thread.h:
* src/systhread.c:
* src/systhread.h: New files.
* src/xgselect.c (xg_select): Avoid using SAFE_NALLOCA and use
xnmalloc unconditionally.
* src/window.c (struct save_window_data): Rename current_buffer to
f_current_buffer.
* src/w32proc.c (sys_select): Change the function signature to
closer fit 'pselect' on Posix hosts.
* src/search.c:
* src/regex.h: Convert some globals to macros that reference
thread-specific values.
* src/process.c (pset_thread, add_non_keyboard_read_fd)
(add_process_read_fd, add_non_blocking_write_fd)
(recompute_input_desc, compute_input_wait_mask)
(compute_non_process_wait_mask, compute_non_keyboard_wait_mask)
(compute_write_mask, clear_waiting_thread_info)
(update_processes_for_thread_death, Fset_process_thread)
(Fprocess_thread): New functions.
(enum fd_bits): New enumeration.
(fd_callback_data): Add 'thread' and 'waiting_thread', rename
'condition' to 'flags'.
(set_process_filter_masks, create_process, create_pty)
(Fmake_serial_process, finish_after_tls_connection)
(connect_network_socket, deactivate_process)
(server_accept_connection, wait_reading_process_output)
(Fcontinue_process, Fstop_process, keyboard_bit_set)
(add_timer_wait_descriptor, add_keyboard_wait_descriptor)
(delete_keyboard_wait_descriptor): Use the new functions instead
of manipulating fd flags and masks directly.
(syms_of_process): Defsubr the new primitives.
* src/print.c (print_object): Print threads, mutexes, and
conditional variables.
* src/lisp.h (enum pvec_type): New values PVEC_THREAD, PVEC_MUTEX,
and PVEC_CONDVAR.
(XTHREAD, XMUTEX, XCONDVAR, THREADP, MUTEXP, CONDVARP)
(CHECK_THREAD, CHECK_MUTEX, CHECK_CONDVAR): New inline functions.
(XSETTHREAD, XSETMUTEX, XSETCONDVAR): New macros.
(struct handler): Add back byte_stack.  Rename lisp_eval_depth to
f_lisp_eval_depth.
* src/eval.c (specpdl_kind, specpdl_arg, do_specbind)
(rebind_for_thread_switch, do_one_unbind)
(unbind_for_thread_switch): New functions.
(init_eval): 'handlerlist' is not malloc'ed.
(specbind): Call do_specbind.
(unbind_to): Call do_one_unbind.
(mark_specpdl): Accept 2 arguments.
(mark_specpdl): Mark the saved value in a let-binding.
* src/emacs.c (main): Call init_threads_once, init_threads, and
syms_of_threads.
* src/data.c (Ftype_of): Support thread, mutex, and condvar
objects.
(Fthreadp, Fmutexp, Fcondition_variable_p): New functions.
(syms_of_data): DEFSYM and defsubr new symbols and primitives.
* src/bytecode.c (struct byte_stack, FETCH, CHECK_RANGE)
(BYTE_CODE_QUIT): Add back.
(exec_byte_code): Add back byte stack manipulation.
* src/alloc.c (cleanup_vector): Handle threads, mutexes, and
conditional variables.
(mark_stack): Now extern; accept additional argument 'bottom'.
(flush_stack_call_func): New function.
(garbage_collect_1): Call mark_threads and unmark_threads.  Don't
mark handlers.
* src/.gdbinit (xbytecode): Add back.

* test/src/thread-tests.el: New tests.
* test/src/data-tests.el (binding-test-manual)
(binding-test-setq-default, binding-test-makunbound)
(binding-test-defvar-bool, binding-test-defvar-int)
(binding-test-set-constant-t, binding-test-set-constant-nil)
(binding-test-set-constant-keyword)
(binding-test-set-constant-nil): New tests.

* doc/lispref/processes.texi (Processes and Threads): New
subsection.
* doc/lispref/threads.texi: New file
* doc/lispref/elisp.texi (Top): Include it.
* doc/lispref/objects.texi (Thread Type, Mutex Type)
(Condition Variable Type): New subsections.
(Type Predicates): Add thread-related predicates.
* doc/lispref/objects.texi (Editing Types):
* doc/lispref/elisp.texi (Top): Update higher-level menus.

* etc/NEWS: Mention concurrency features.

diff --cc etc/NEWS
Simple merge

diff --cc lisp/subr.el
Simple merge

diff --cc src/Makefile.in
Simple merge

diff --cc src/bytecode.c
Simple merge

diff --cc src/data.c
Simple merge

diff --cc src/emacs.c
Simple merge

diff --cc src/eval.c
Simple merge

diff --cc src/lisp.h
Simple merge

diff --cc src/process.c
Simple merge

diff --cc src/w32.c
Simple merge

diff --cc src/window.c
Simple merge