Shared Library Changes for Release 2.1.2

Shared library libddcutil is backwardly compatible with the one in ddcutil 2.0.0. The SONAME is unchanged as libddcutil.so.5. The released library file is libddcutil.so.5.1.0.

It also fixes several minor bugs and has internal changes to better accomodate the proprietary Nvidia diver

Changed Functions	Comments
ddca_start_watch_displays	Requires that all video drivers implement DRM
ddca_get_sleep_multiplier	Revert to release 2.0.0 semantics
ddca_set_sleep_multiplier	Revert to release 2.0.0 semantics