Fix bug #8562 with Emacs display on Windows 9X.

Fix bug #8562 with Emacs display on Windows 9X.
Thanks to oslsachem <oslsachem@gmail.com> for helping to debug this.

 src/w32font.c (g_b_init_is_w9x, g_b_init_get_outline_metrics_w)
 (g_b_init_get_text_metrics_w, g_b_init_get_glyph_outline_w)
 (g_b_init_get_glyph_outline_w): New static variables.
 (GetOutlineTextMetricsW_Proc, GetTextMetricsW_Proc)
 (GetGlyphOutlineW_Proc): New typedefs.
 (w32_load_unicows_or_gdi32, get_outline_metrics_w)
 (get_text_metrics_w, get_glyph_outline_w, globals_of_w32font): New
 functions.
 (w32font_open_internal, compute_metrics): Call
 get_outline_metrics_w, get_text_metrics_w, and get_glyph_outline_w
 instead of calling the "wide" APIs directly.
 src/emacs.c (main) [HAVE_NTGUI]: Call globals_of_w32font.
 src/w32.h (syms_of_w32font): Add prototype.