Add files to help manage the (vga) syscons mouse cursor.

To mostly fix distortion of mouse cursors by non-square pixels, I
needed 8 variants of the same cursor shape for large fonts and
another 7 variants for small fonts. Some variants are shared,
leaving only 13 variants in 26 glyphs altogether. Keep these in
the BDF source file cursor.bdf. cursor.bdf has another 5 unused
experimental cursors in 10 glyphs. cursor.awk is a simple awk
script for converting this and similar bdf files into C declarations
for copying into scvgarndr.c. syscons doesn't use any of this yet.