Simplify recording of main thread's ID on MS-Windows
* src/w32term.c (w32_initialize):
* src/w32console.c (initialize_w32_display):
* src/w32fns.c (globals_of_w32fns): Don't record the main thread
ID independently for each type of session (GUI, TTY, batch).
* src/w32term.c (w32_init_main_thread): New function, records the
main thread's thread ID.
* src/w32term.h: Add prototype for w32_init_main_thread.
* src/emacs.c (main) [WINDOWSNT]: Call w32_init_main_thread.
* src/emacs-module.c [WINDOWSNT]: Rename main_thread_id to
main_thread, for consistency with other threading libraries. All
users changed. Include w32term.h.
(check_main_thread) [WINDOWSNT]: Simplify the test: no need to
make sure the main thread is alive, as we hold a handle on it
opened by w32_init_main_thread.
(module_init) [WINDOWSNT]: Reuse the thread ID recorded by
w32_init_main_thread, instead of calling the requisite APIs once
more.