Build k2crypt.dll for OS/2

[davidrg]

This requires building libdes with Open Watcom, something we don't currently bother doing on either Windows or OS/2. The code is likely compatible enough with Open Watcom, but Watcoms nmake clone doesn't like the makefile.

[jmalak]

I don't know if relation to Open Watcom Microsoft tool clones is right way.
Probably best solution is to abandone this and use Open Watcom directly to enable full-cross compile features for any supported host as Windows/Linux/OSX/OS/2.
Especially Microsoft tools have various options per version but Open Watcom has very stable command line interface that no changes is required for command line with different version of Open Watcom. It is also independent on host system because Open Watcom is by nature cross-compiler.
Also native wmake make files can be independent on host that single simplified make file can handle all build hosts and build targets.
This is example of porting Open Zinc to Open Watcom 2.0 and building on Windows/Linux/OSX(Intel)/OSX(ARM) by Open Watcom 2.0 for 32-bit DOS, 16-bit Windows, 32-bit Windows and 32-bit OS/2.