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.

When we didn't find the filesystem in /proc/mounts, we would go
through /etc/mtab, but then completely botch the parsing thereof.
Move the parsing to a common function to avoid this problem.

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.

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.

Assemble all files to ELF instead of using the NASM built-in linker.
This can enable us to do actual linking in the future.

Use $(CC) in gcc_ok macro, not plain gcc.  This seems to work, iff the
gcc_ok macro is declared with =, not :=

Some old distros would have <linux/fs.h> poison the namespace with a
non-glibc "struct statfs".  Hack around it.