[Media_api] Portmidi update -- VC++ files added

[Roger Dannenberg]

I omitted some VC++ project files and a "solution" file from the recent
release, so I just added them and put a new zip file on the web. The
date/version and the portmidi web page have all been updated to
portmidi28aug06.zip.

Also, the documentation is not clear about makefiles, which are
pm_mac/Makefile.osx and pm_linux/Makefile. You should either copy the
makefile you want to portmidi/Makefile and run make in portmidi, or specify
the makefile you want, e.g.

make -f pm_linux/Makefile

-Roger