(w32_fill_rect): Do not try to deal with NULL hdc

(w32_fill_rect): Do not try to deal with NULL hdc
here. Callers changed to always pass real device context.
(w32_draw_bitmap): Likewise.
(w32_get_glyph_overhangs): Likewise.
(w32_draw_box_rect): Make use of s->hdc rather than getting a new one.
(w32_set_vertical_scroll_bar): Pass correct HWND parameters to
pfnSetScrollInfo and SetScrollRange.
(x_get_char_face_and_encoding): Don't turn iso8859-1 characters
back into MULE characters after decoding them.
(x_get_glyph_face_and_encoding): Likewise.
(w32_per_char_metric): Use GetCharExtentPoint32W as fallback when
GetCharABCWidthsW fails, since this is defined on Windows 9x.
(x_produce_glyphs): Calculate per char metrics for a character
that we know exists in default font when font_not_found_p is true.