Hitting Ctrl-U deletes to the beginning of the line, but hitting Ctrl-Y
afterward yanks a truncated and mangled string.  Looking at the
code (in grub-core/normal/cmdline.c), it looks like the implementation
of Ctrl-U never got converted from 8-bit characters to UCS-4, so it only
copies N bytes rather than N characters.  The attached patch fixes this
problem.

Changelog entry for this patch:

2013-05-27  Josh Triplett  <josh@joshtriplett.org>

        * grub-core/normal/cmdline.c (grub_cmdline_get): Fix Ctrl-u
        handling to copy the killed characters to the kill buffer as
        UCS4 stored as grub_uint32_t rather than as 8-bit characters
        stored as char.  Eliminates UCS4 truncation and corruption
        observed when killing characters with Ctrl-u and yanking them
        back with Ctrl-y.

I've also attached the patch in "bzr send" form for direct application,
including the changelog entry.