Also initialize byte-compile-noruntime-functions between runs.

bytecomp.el (byte-compile-new-defuns): New variable.
(byte-compile-initial-macro-environment): For eval-when-compile: bind
byte-compile-unresolved-functions and byte-compile-new-defuns around
byte-compile-top-level, to prevent spurious entries being made.
(byte-compile-warn-about-unresolved-functions): Check whether function is in
byte-compile-new-defuns before emitting a warning about it.
(byte-compile-from-buffer): Initialize new variable and
byte-compile-noruntime-functions to nil.
(byte-compile-file-form-require): record all new functions defined by a
`require' in byte-compile-new-defuns.
(byte-compile-file-form-defmumble): record the new alias in
byte-compile-new-defuns.

* 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.

* lisp/mpc.el (mpc-format): Leave dir as relative path

* src/window.c (grow_mini_window, shrink_mini_window): Set the
frame's 'window_sizes_changed' flag.
* src/xdisp.c (redisplay_internal): Call the hooks on
'window-size-change-functions' if the call to 'echo_area_display'
sets the frame's 'window_sizes_changed' flag.
(syms_of_xdisp) <window-size-change-functions>:
Update doc string to indicate the mini-window resizes trigger a
call to the hooks, and don't promise that will happen "before
redisplay".  (Bug#19576, Bug#21333)

* doc/lispref/windows.texi (Window Hooks): Update the description
of 'window-size-change-functions'.

* src/fns.c (Frequire): Doc fix to include the dynamic module
support.
* src/lread.c (Fload, Vload_suffixes): Doc fixes to include the
dynamic module support.
(Fload): Treat the module suffix the same as '*.el' and '*.elc'
wrt the MUST-SUFFIX argument.

* etc/NEWS: Expand documentation of dynamically loaded modules.

* etc/NEWS: Mention the new support for dynamically loaded modules.

Copyright-paperwork-exempt: yes

* lisp/progmodes/xref.el (xref-backend-functions): Move the
default value into a separate `add-hook' call (bug#21964).

* lisp/progmodes/elisp-mode.el (emacs-lisp-mode):
Don't declare the xref-backend-functions variable.
It doesn't make any difference.

* src/emacs-module.c (module_free_global_ref): Add a FIXME
comment about error reporting.  Fix a recently-introduced typo
that double-decremented the refcount.

* src/emacs-module.h (emacs_module_init): New decl.
Without it, GCC might complain about a module that defines
emacs_module_init without using it.  This also checks the
API better.