Threading: Scrubbed usage of threading in libraries

Removed include for pthreads from libraries where it appears NOT to be
used.  Added ${CMAKE_THREAD_LIBS_INIT} to CMakeLists.txt for libraries
which appear to require threading.

Signed-off-by: Noel Eck <noel.eck@intel.com>

src/mma7455/mma7455.cxx

@@ -28,7 +28,6 @@
 #include <unistd.h>
 #include <stdlib.h>
 #include <string.h>
-#include <pthread.h>
 #include <math.h>
 
 #include "mma7455.hpp"