[base] Allow renderers of different formats.

* src/base/ftobjs.c (FT_Render_Glyph_Internal): Do not return if the
glyph's slot format is `FT_GLYPH_FORMAT_BITMAP`.  The forthcoming
'bsdf' renderer will require bitmaps for processing.

* src/base/ftobjs.c (ft_add_renderer, ft_remove_renderer): Remove
renderer's glyph format check before adding and removing them.  The
'bsdf' renderer will have a format `FT_GLYPH_FORMAT_BITMAP`.
2 files changed