* dispextern.h: Change HAVE_X_WINDOWS to HAVE_WINDOW_SYSTEM,

* dispextern.h: Change HAVE_X_WINDOWS to HAVE_WINDOW_SYSTEM,
around image definitions and prototypes.
(gamma_correct) [WINDOWSNT]: New prototype.

* w32term.c (x_make_frame_visible): Replace call to
input_poll_signal with poll_for_input.

* window.c [WINDOWSNT]: Include w32term.h.

* xdisp.c [WINDOWSNT]: Include w32term.h.

* makefile.nt: Add dependencies on w32gui.h.
(OBJ1): Include atimer.obj.
($(BLD)\atimer.obj): New dependency rule.

* w32.c (sigmask): New function (does nothing).
(sigunblock): Ditto.

* frame.c [WINDOWSNT]: Include w32term.h.

* w32gui.h (struct W32FontStruct): Add ascent and descent slots.

* lread.c (syms_of_lread): Fix literal newlines.

* emacs.c (USAGE): Split into USAGE1 and USAGE2, to work-around
the string constant limit (2048 bytes) in MSVC.
(main): Ditto.