(w32_get_bdf_glyph): Cast between unsigned char and char when
passing arguments to subroutines, to shut up compiler warnings.
(w32_get_bdf_glyph): Don't mix signed and unsigned when calling
GET_HEX_VAL.
(get_quoted_string): Fix limit on memchr search.
(set_bdf_font_info): Use unsigned chars. Negate yoffset.
(w32_init_bdf_font): Initialize codepoint and bitmap heaps.
(w32_free_bdf_font): Free bitmaps and codepoints on heaps.
(get_cached_font_char, cache_char_offset): Use macro
BDF_CODEPOINT_RANGE_COVER_P.
(cache_char_offset): Use HeapAlloc to allocate codepoints on own heap.
(clear_cached_bitmap_slots): New function.
(GET_HEX_VALUE): G-Z, g-z are not hex.
(w32_get_bdf_glyph): Convert to DIB format. Return bytes read.
(get_bitmap_with_cache): Use new cache implementation.
(create_offscreen_bitmap): New function.
(w32_BDF_TextOut): Use it. Draw glyphs as DIBs.
(get_bitmap_with_cache): Check if CreateBitmap failed.
Adjust cache size dynamically so cache is never larger than the
system limit of GDI resources.
Do cache clearing inline. Move global variables to local scope.
