This is an initial attempt at a regression testing framework.

Initially it has some regression tests that come from the work on
improvements to the msg box.

The framework allows the tests themselves to remain extremely simple. They
just need to send a number and potential error message to the outlet.

However, they do need to be added in the main patch. This is because we
will need to run some tests in a certain order. We could number the test
filenames but that's less easy to change later.

This reverts commit ddfbb4f5.

revert to using a single way for finding the libdir, as my assessment of the OSX bug turned out to be wrong

* the original namespace-collision checker only worked for abstractions
* trying a new namespace-collision checker revealed about 80 new clashes.
  Since there are so many it's probably too disruptive to remove them.
* probably need to revert the namespace clash abstraction removals

repo cleanup: remove tcl/tk build infrastructure and scripts, old patches, automated build scripts for pd-extended, old gui plugins, and unnecessary install-time dependencies

Add missing dlls to Windows installer, add dynamic lib extensions for Windows and OSX to scripts/load_all_binaries.pd