Attempt to fix crashes due to accesses beyond glyph matrix end
* src/xdisp.c (x_produce_glyphs): When it->ascent and it->descent
are determined from per-character metrics, don't let the
max_ascent and max_descent become smaller than values returned by
normal_char_ascent_descent, to avoid unpleasant dynamic resizing
of screen line heights when text changes.
* src/xterm.c (x_new_font)
* src/w32term.c (x_new_font): Call get_font_ascent_descent to
obtain a reasonable value for FRAME_LINE_HEIGHT, even when a font
claims very large value for its height.
* src/font.c (font_open_entity): Call get_font_ascent_descent to
obtain a reasonable value for FRAME_SMALLEST_FONT_HEIGHT, even
when a font claims very large value for its height.