Include w32term.h and w32heap.h.

Include w32term.h and w32heap.h.
(map_keypad_keys):
(Vw32_enable_caps_lock):
(Vw32_enable_num_lock):
(Vw32_pass_lwindow_to_system):
(Vw32_pass_rwindow_to_system):
(Vw32_lwindow_modifier):
(Vw32_rwindow_modifier):
(Vw32_apps_modifier):
(Vw32_scroll_lock_modifier):
(w32_key_to_modifier): Add externs.
(w32_kbd_mods_to_emacs): Recognize Windows keys, Apps key, and
Scroll Lock as potential modifiers; exclude numpad keys from
effect by CapsLock; act on Vw32_enable_caps_lock; remove obsolete
code.
(is_dead_key): Copy from w32fns.c.
(w32_kbd_patch_key): Comment attempt to improve handling of
dead-keys, and system bug relating to same on Windows NT.  Work
around the bug by calling ToUnicode and then converting to the
correct codepage.
(map_virt_key): Removed obsolete variable.
(lispy_function_keys): Add extern.
(key_event): Major rework of keyboard input handling: optionally
recognize Windows keys and Apps key as modifiers; optionally treat
NumLock, CapsLock and ScrollLock as function keys; let system
translate keystrokes to characters to avoid system bugs relating
to dead-key handling; preserve shift distinction for control
characters.  Remove some obsolete code.