clean up Makefile for tests directory
clean up Makefile for tests directory

- remove definition and use of LOCALEDIR since this is not used anywhere
  in the tests
- change AM_CFLAGS to AM_CPPFLAGS since these flags should really be
  CPPFLAGS
- replace autoconf substitutions with make variables

Reviewed-by: Andrei Kholodnyi <8ed355542eeb21dc16259915650192a25bd4bf1a@gmail.com>

use INCLUDES instead of inc_c_api
remove inc_local, since only clientlib headers shall be used

Modified-by: Andrei Kholodnyi <8ed355542eeb21dc16259915650192a25bd4bf1a@gmail.com>

razr/speechd,razr/speechd,razr/speechd,razr/speechd