Prevent assert at frame.c, l. 6311 by initializing glyph cachels. * frame.c (Fmake_frame): Ensure that reset_glyph_cachels gets called. (setup_minibuffer_frame): Improve header comment. * redisplay.c (redisplay_window): Update comment. Remove code checking for uninitialized face_cachels and glyph_cachels. Can't happen in theory, and guarded by asserts in practice. * window.c (allocate_window): Update comment on reset_*_cachels.