- Adapted Makefile to customized pkg-config.

 - Update config files.

 - Changed version number to "0.7.0-b6".

 - Made interface methods static.
 - Implemented "get_config_value" and "get_config_option_names".

 - Added math library to compilation libs.

 - Adapted to pkg-config.
 - Cleaned up config.*.mk files.
 - Fixed screen struct interface.

 - Raised version number for read_char-implementation.

 - Added ENABLE_READCHAR_VIA_TERMIOS option to configuration files.

 - Implemented read_char in two variants, one using standard, general
   C-compliant fgetc, one using termios.

 - Fixed complication argument order.
 - Added "-f" flag to rm in clean target to suppress warnings.

 - Raised version number for trace-fix and compilation error due to
   missing stream.h
 - (Second raise due to forgotton "b2" increment.)

 - Raised version number for trace-fix and compilation error due to
   missing stream.h.

 - Added #ifdef ENABLE_TRACING around turn_on_trace().
 - Added forgotten streams.h inclusion.

 - Fixed install directory to use $(HOME) instead of hardcoded path.
 - Disabled tracing by default.