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>

src/ds18b20/ds18b20.cxx

@@ -25,6 +25,7 @@
 #include <iostream>
 #include <time.h>
 #include <stdexcept>
+#include <syslog.h>
 
 #include "ds18b20.hpp"
 
@@ -214,6 +215,9 @@ float DS18B20::readSingleTemp(int index)
     case RESOLUTION_9BITS: frac &= 0x08; break;
     case RESOLUTION_10BITS: frac &= 0x0c; break;
     case RESOLUTION_11BITS: frac &= 0x0e; break;
+    default:
+        syslog(LOG_WARNING, "%s: switch case not defined",
+            std::string(__FUNCTION__).c_str());
     }
 
   // remove the fractional with extreme prejudice