[c86] Build and copy C86 toolchain automatically to ELKS /root

[ghaerr]

This PR adds a script that will build the entire C86 toolchain from scratch, and and another that will copy all required headers, libraries and example source files to ELKS /root so an image can easily be made to test running C86.

Usage:

(edit and run '. env.sh', '. wcenv.sh' and '. c86.sh' first to set TOPDIR=, WATCOM= and C86= environ vars)
$ ./buildc86.sh     # builds host and native ELKS toolchain and libraries
$ ./copyc86.sh     # copies libraries, headers and examples to /root
$ make kimage     # quickly build image (must be 2880k or larger, won't fit on 1440k floppy)