Update amalgamation of dr_wav.

With this change, dr_wav is now namespaced with "ma" which means dr_wav
can now be used alongside miniaudio.

In addition, some duplicate code has been removed, such as sized types,
result codes, allocation callbacks, etc. which reduces the size of the
file slightly.

This should address the following public issue:
  https://github.com/mackron/miniaudio/issues/673