[Tinymux] Support for Windows 95, 98, 98SE, Me, and NT 4.0 in TinyMUX 2.6

[Stephen Dennis]

I ended up not disabling Windows 95/95OSR2/98/98SE/Me support,
however, I really don't have a good way of testing it, and haven't for
some time. To help a bit with the testing, I added the -n command-line
option to netmux.exe which disables use of NT I/O Completion ports
making the 9x code paths reachable.

I'm also not sure how far back the Intel compiler goes.

Windows 95 ran on 386DX. Maybe I can find a copy a Windows 95 and
bring it up with VMWare for grins.

Brazil