Startup prefs: lots of dialog data causing issues on OSX when transmitting from GUI to engine

To reproduce: open the prefs dialog on OSX, hit Ok => spurious error message error: mento: no such object in the console (which obviously comes either from the /Applications/Pd-l2ork-full-x86_64-20161113.app/Contents/Resources/app.nw/extra/memento entry in the search paths or the memento entry in the startup libraries).

This isn't a whitespace issue. I've tested search paths with embedded blanks -- sending these to the engine does work fine (on Linux at least), and the code properly encodes the pathnames using the dialog-save encoding before submitting them. Also, the error message changes when trying to insert a search path at the beginning of the table.

So it seems that lots of dialog data (which translates into lots of string arguments for pd_send and thus lots of string data being submitted over the socket) causes issues with pdgui.pd_send on some platforms (this doesn't happen on Linux); might be caused by socket buffer limits.

Possible solution: Transmit the search paths and startup libraries data one-by-one. Tedious and slow, but doable.

This should be considered a release blocker (#220 (closed)). Working on it...