Vacuous ADV support: install an empty ADV.

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

Merge the SYSLINUX and EXTLINUX patching code and core code, removing
EXTLINUX as a separate derivative.  All the disk-based systems now use
the same code.

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

Reduce sector 1 space pressure by moving objects that aren't needed by
Sector 1 proper into an "extended patch area".  While we're mucking
with the installer code, make the syslxint and extlinux installer code
even more similar.  It should now be pretty straightforward to
outright merge the code.

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

Move copybs to dosutil, change the Makefile to deal with UPX being
able to compress (e.g. very small files.)

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

Resolved Conflicts:
	com32/Makefile
	com32/lib/sys/open.c
	com32/modules/Makefile
	dos/Makefile
	dos/com16.ld
	dos/syslinux.c
	version

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

int 25h and int 26h are known to be register-dirty for some versions
of DOS -- unlike int 21h, which is usually clean.  As such, wrap those
in assembly functions.

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

My version of the linker can deal with it, but others might not be so
smart.

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

gcc will produce an .eh_frame section, which we have no use for.

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

At least under WinME, the DOS installer did not work as advertised.
With these modifications, it seems to work okay.

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