Warning free build achieved for most platforms

[Pavel Roskin]

Hello!

As of now, GRUB builds without warnings for all platforms except
i386-coreboot.  The build is done using gcc 4.4.0 for i386 and x86_64
and gcc 4.3.3 for PowerPC and SPARC64.

Actually, the coreboot warnings should really be errors.  In particular,
kern/i386/coreboot/init.c calls grub_at_keyboard_init(), which is not
defined anywhere.  It looks like that the coreboot code needs to be
ported to the new terminal handler code.

Also, I noticed that escape sequences are not processed correctly in the
serial code on i386-pc.  The fix would be to wait a little bit after the
input bytes arrive to see if they would make an escape sequence.  The
problem is still there, but I decided to fix the warning anyway to
encourage warning-free code.

If we want to use -Werror, now it's the time.  In fact, it would be good
for the coreboot code too, as its warnings are actually errors.

-- 
Regards,
Pavel Roskin