Don't include gnu.h.

Don't include gnu.h.
(x_io_error_quitter, x_draw_image_foreground_1): Remove prototypes.
(x_sync): Move to macfns.c.
[USE_CG_DRAWING] (mac_define_fringe_bitmap): Remove unused
variable `mask_bits'.
(mac_compute_glyph_string_overhangs): Avoid ambiguous `else'.
(x_draw_image_glyph_string): Remove unused variable `pixmap'.
(x_mac_to_emacs_modifiers): Remove function.
(XTset_vertical_scroll_bar, mac_handle_visibility_change)
(x_make_frame_visible, xlfdpat_create, mac_handle_command_event):
Add explicit braces to avoid ambiguous `else'.
(x_make_frame_visible): Remove unused variables `type',
`original_top', and `original_left'.
(mac_do_list_fonts, XTread_socket): Add parentheses around && within ||.
(x_load_font): Remove unused variables `full_name', and `value'.
(do_get_menus, do_init_managers, do_check_ram_size) [!MAC_OS8]:
Remove functions.
(do_zoom_window): Reorganize variables with respect to conditionals.
(init_command_handler): Remove unused variable `err'.
[MAC_OSX] (mac_check_bundle): Remove unused variable `child'.