Log Message:
Update pmw to 4.29

Version 4.29 26-June-2016
-------------------------

1. Added -norc to the scripts for running tests to ensure that the user's
   .pmwrc file, if it exists, is ignored.

2. Running with a lot more compiler warnings turned on threw up a number of
   infelicities in the code. Refactoring has got rid of the compiler warnings.

3. Compiling with clang threw up a few that gcc missed; it also found a genuine
   bug, a misplaced ) in an expression. By pure fluke there appeared to be no
   way of provoking misbehaviour, because what was being checked was re-checked
   (correctly) later.

4. Allow ! as a modifier to notes as well as rests.