One more attempt at getting semi-sanity to "make install".
Realistically, the install/netinstall/install-all/... needs to be
pushed into the com32 Makefiles, but this is at least a quick hack.

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

Make the new MBR variants installables, and add to the NEWS file.

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

Add com32/hdt/*.c32 to the list of installables, thereby making
hdt.c32 an installable.

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

Add modules directory to BSUBDIRS.

Add the pxechain module from Jeffery Hutzelman at CMU.
Create new modules directory for non-com32 modules.
Centralize installation, since we have three types of install, and
only one of them was distributed.

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

Cleanup and centralize the Makefile system even more.
Fix a gcc 4.3 incompatibility in memdisk (definition of strlen).

Centralize more (most) of the version number machinery to version.pl.

Clean up the BSUBDIR/ISUBDIR separation further.  Build _bin.c files,
which are an intermediate stage toward building the installers, in the
libinstaller directory, since that directory is used by all the
installers anyway.  That also lets us get bin2c.pl out of the root.

- "make clean" should not clean up things that "make installer" cannot
  regenerate.
- "make installer" should not descend into subdirectories which are
  target only, e.g. com32 and sample.

The Linux platform stuff in com32 is old and bitrotted, and was only
for debugging in the first place.  Just ignore it.