(w32_load_system_font, w32_to_x_charset): Use strnicmp

(w32_load_system_font, w32_to_x_charset): Use strnicmp
in place of stricmp.
(w32_list_synthesized_fonts): Removed.
(w32_to_all_x_charsets, enum_font_maybe_add_to_list): New functions.
(struct enumfont_t): New element; list.
(enum_font_cb2): List all style and charset variations of a font.
(Fw32_select_font): New optional argument; include_proportional.
Exclude vertical fonts.  Exclude proportional fonts unless
include_proportional is non-nil.
(w32_enable_synthesized_fonts): Change to a boolean.
(Fw32_send_sys_command): Doc fix.