Make sure we don't trash a useful value in errno.

Conflicts:

	NEWS
	com32/modules/Makefile

Rewrite the algorithm to prefer entries which can be directly moved
into their target slots; this should reduce the number of descriptors
in most cases (although not necessarily *all* cases.)

Try to clean up the code some while we're at it... the code is
confusing enough as it is.

The old code could fail to coalesce backwards in the case where a
range is totally obliterated.  For now, just scan the whole list.

Use the syslinux_memmap data structure for the free memory list.  This
means we get range coalescing; this sometimes generates lists that are
vastly shorter than without range coalescing.

Handle the case of an upward move when there is something in the way.
This happens when loading an SDI image.

Add stpcpy(), and actually implement syslinux_version() and
syslinux_derivative_info().

Add zopen(), zfopen(), and zloadfile() to transparently open and
uncompress a gzip file (adding support for other formats is quite
trivial.

Once a file handle or file pointer is received, it can be treated like
any other one (fstat will report it as a socket, since the length is
unknown.)

Handle unspecified file length for comboot/com32 modules; do changes
to the appropriate part of libcom32 to handle this properly.