[PATCH 1/8] clean up Makefile for c api

[Andrei Kholodnyi]

> Thanks William.
> This series is pushed with a minor modifications.

William has asked me to describe modifications I did, so here we go.

All modifications are listed in commits.

Here is a short summary:

there was one bug in your patch
- $(inc_audio)$(ibmtts_include)  were written together
- you have added $(top_srcdir)/include in clients and tests and I have
removed it since these are client programs.
- I have also used INCLUDES instead of inc_local where applicable.

Andrei.