Werror: Enable warnings as errors

Added C/CXX warning messages similar to MRAA (w/ -Werror).

    * Added syslog warning for missing switch cases
    * Cleaned up uint vs int usage
    * Fixed redifinition errors for C structs
    * Added virtual destructors for base classes
    * Removed redundant CMAKE_CXX_FLAGS from COMPILE_FLAGS for all three
      wrapper languages.  The CMAKE_CXX_FLAGS were showing up twice in
      the compile commands for the wrappers.
    * Added CMake WERROR option to enable/disable warnings as errors for
      all targets.
    * Disable a handful of compiler warnings for the wrapper cxx files,
      this minimizes the number of warnings from auto-generated code).

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

examples/c++/pulsensor.cxx

@@ -43,7 +43,7 @@ sig_handler(int signo)
 
 void
 handler (clbk_data data) {
-    printf ("callback data (%d)\n", data);
+    printf ("callback data (%d)\n", data.is_heart_beat);
 }
 
 int
@@ -51,7 +51,7 @@ main(int argc, char **argv)
 {
 //! [Interesting]
     Pulsensor *sensor = new Pulsensor(handler);
-    
+
     sensor->start_sampler();
     while (!doWork) {
         usleep (5);