Make vga_write_string() and vga_write() handle newlines.
Add emit_formatted() to lib.

Eventually, this function will play a role similar to printfmt.

Right now, it doesn't actually do any formatting.  It even ignores all
the data, for now!
Implement cprintf!

And, replace vga_write_string() calls with cprintf() calls.
Write skeleton for handling args in emit_formatted_var.

Only escaped percentages, e.g. "100%%", are actually implemented.
Implement half-baked emit_formatted_var().
Make demo_cprintf functions.
Make emit_formatted_var default fill character a space.
Remove length-fixing (originally for demo purposes).
Implement strlen.
Implement string printing for emit_formatted_var.
Fix issue causing data stream not to be consumed.
Fix spacing.
Implement strrev.
Factor out padded-buffer printing.
Consume filler *before* length.
Implement hex number printing.
Update kernel demo functinos to use cprintf for displaying numbers.
Add unsigned decimal number printing to emit_formatted_var.
Merge pull request #1 from jasonpr59/cprintf

Implement cprintf(), via emit_formatted_var().