Added the mraa_strresult function

Signed-off-by: Jefferson Lee <jeffersonlee2000@gmail.com>

api/mraa/common.h

@@ -190,6 +190,13 @@ int mraa_set_priority(const int priority);
  */
 const char* mraa_get_version();
 
+/**
+ * Returns a textual representation of the mraa_result_t
+ *
+ * @param result the result to stringify
+ */
+const char* mraa_strresult(mraa_result_t result);
+
 /**
  * Print a textual representation of the mraa_result_t
  *