The code portability will be provided through the autotools build
system. Any additional portability code will be provided in the
top-level source structure along side the other code (e.g. `src/compat`).

This creates an fread compatible API on wxInputStream objects and
uses that API in LoadSpectSeq. This is to help the transition from
the wxWidgets wxInputStream API to the C FILE API.

This removes the GUI part of espeakedit, keeping the part that is
responsible for compiling the voice and intonation data. The
motivation for this is:

  1.  the voice and intonation data compilation will move into
      libespeak-ng after removing the wxWidgets logic and converting
      the code to C;

  2.  the espeakedit code is tightly coupled to the internals of
      libespeak-ng at a source code level, not a binary/API level,
      making the code harder to maintain;

  3.  a new GUI will be written in Qt that better supports creating
      and editing voices and languages.

This is part of the process of making compiledata.cpp independent
of espeakedit.

This is part of the process of making compiledata.cpp independent
of espeakedit.