Improved support for IBM operating systems

Fix compiler errors and warnings when building on IBM operating systems such as AIX and IBM i.

json_c_version.h

@@ -12,6 +12,10 @@
 #ifndef _json_c_version_h_
 #define _json_c_version_h_
 
+#ifdef __cplusplus
+extern "C" {
+#endif
+
 #define JSON_C_MAJOR_VERSION 0
 #define JSON_C_MINOR_VERSION 14
 #define JSON_C_MICRO_VERSION 99
@@ -44,4 +48,8 @@ JSON_EXPORT const char *json_c_version(void); /* Returns JSON_C_VERSION */
  */
 JSON_EXPORT int json_c_version_num(void); /* Returns JSON_C_VERSION_NUM */
 
+#ifdef __cplusplus
+}
+#endif
+
 #endif