Fix -Wall compiler warnings in MSDOS sources.

Fix -Wall compiler warnings in MSDOS sources.

 msdos.c (IT_set_face): Fix format string to match argument types.
 (IT_write_glyphs, IT_note_mode_line_highlight)
 (IT_set_frame_parameters): Remove unused variables.
 (x_set_menu_bar_lines): Declare set_menu_bar_lines.
 (IT_set_terminal_modes): Disambiguate expression in if clause.
 (Fmsdos_remember_default_colors): Return Qnil.
 (IT_set_frame_parameters): Add parens to disambiguate boolean
 expression for logging the cursor type to termscript.
 (keyboard_layout_list, keypad_translate_map)
 (grey_key_translate_map): Add braces in inner initializers.
 (dos_rawgetc): Add parens in condition for mouse-3 button-press.
 (dos_rawgetc): Remove unused label.
 (XMenuActivate): Add braces to remove ambiguous `else'.
 (dos_ttraw): Always return a value.
 (spawnve): Declare.
 (run_msdos_command): Cast 3rd arg of spawnve to "char **".
 dosfns.h (x_set_title): Declare.
 w16select.c (Fw16_set_clipboard_data, Fw16_get_clipboard_data):
 Remove unused variables.
 dosfns.c (Fint86, Fdos_memget, Fdos_memput): Remove unused variables.
 (init_dosfns): Declare get_lim_data.
 (system_process_attributes): Declare Fget_internal_run_time.