Files that should have been added before...

Allow "boot" as the drive specification; this can be used both with
partition numbers and with loaders.

gpxe/src/Config versus gpxe/src/config is a problem on case-deficient
filesystems; update to top of tree gPXE so we don't have that problem
anymore.

It seems to make more sense to put the console codepage first, since
it is the more significant of the two codepages.  It also makes more
sense in the from..to sense.

Make sure we create the /etc directory before putting something there.

After all, "make dist" is about producing the wrapped binaries for
release.

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.

There are some build fixes which may be relevant, so pull in the
latest gPXE git.

To avoid confusion during subdirectory make, make the undionly.kpxe ->
gpxelinux.0 conversion an explicit rule.