Use a better malloc for the core.  In particular, use the same core
that we should eventually be able to use for the entire system in
Syslinux 5 -- with module awareness, etc.

This code can also accommodate multiple heaps.  Set up a separate heap
for lowmem; the intent is to use explicit lowmem allocations instead
of the static bounce buffer.  The lowmem allocation is also exported
via the pmapi mechanism, so modules can safely allocate lowmem.

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

Resolved Conflicts:
	com32/Makefile
	com32/include/syslinux/pxe.h
	core/pxelinux.asm
	core/syslinux.ld

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

Another attempt at unify protected mode entry/exit, based on the
previous bcopyint branch.  This should, among other things, give a
"full service" PM environment including BIOS upcalls and interrupt
service to the core-internal code.

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.