Build files: removed a bunch of make rules for long-dead unsupported systems
...in order to unify and simplify the build. If a need to support this
ancient systems arose, these hacks may ni longer be needed (due to new
versions of tools) or the hacks would have to be written again (better)
or retrieved from SCM (worse). Time will show.
nmake /nologo -f nt.mak
nmake /nologo -f ntw.mak
nmake /nologo -f ntx.mak