[Media_api] Core Midi empty port name problems

[Roger Dannenberg]

I just committed revisions that, based on fixes and testing by Angus 
Hewlett and Rob King should correct some problems with SMPTE time code 
messages and EndPoint names under OS X. There was also a change to some 
filter definitions, so if you were doing anything fancy with 
PM_FILT_CLOCK and PM_FILT_PLAY, you might want to check to see if I 
either broke (or fixed!) your code.

I've done zero additional testing, but I thought it was best to at least 
commit the changes to SVN. I'm in the process of getting some help to 
compile and test everything on 3 platforms before putting this version 
out as a (non-SVN) downloadable zip file.

We also hope to soon have John Harrison's pyPortMidi source integrated 
into the PortMedia project on Sourceforge.

-Roger