Set .bss and .uibss as soon as we are fully loaded.  This gives us the
more familiar behavior of most normal execution environments.  The
.earlybss section is not zeroed; therefore, all variables that are set
before we have the opportunity to zero need to go in this section.

This checkin also fixes some incorrect section directives.

Signed-off-by: H. Peter Anvin <hpa@zytor.com>

Move source files out of the root directory; the root is a mess and
has become virtually unmaintainable.  The Syslinux core now lives in
core/; the Linux and generic utilities has moved into utils/, and
copybs.com has moved into dos/; it had to go somewhere, and it seemed
as good a place as any.