[tools] Add omf2elf, omfdump and os2toelks object file utilities

[ghaerr]

Adds omf2elf which converts Watcom .OBJ 16-bit OMF output object files to ELKS-compatible .o files.
Adds omfdump to display OMF file internal contents.
Adds os2toelks which converts OS/2 v1.x 16-bit executables to ELKS a.out executable format.

The omf2elf utility is being used to convert OBJ output from OpenWatcom C to ELF .o file format, for linking against ELKS C library to produce an ELKS executables.

The os2toelks utility can be used to convert16-bit OS/2 v1.x executable programs created using Watcom C (using -bos2) to ELKS a.out executable format. This is currently less useful than using omf2elf and recompiling because the system calls likely present in OS/2 executables are not compatible with ELKS and can't be converted. In the future, should OpenWatcom C's C Library be updated to support 16-bit Linux (ELKS), then this option could work well, as Watcom doesn't currently create a.out executables.

The conversion utilities come from some very interesting projects. omf2elf is enhanced by this PR to support 16-bit OMF OBJ file support.

OMF2ELF: Minilibc686 Project.
OMFDUMP: Omfdump.

Coming later will be an OpenWatcom owcc C compiler wrapper script to allow compatible compilation of C files for linking against ELKS' C Library and producing ELKS executables.