Merge branch 'candidate-5.0.6' into candidate-5.2.0

Signed-off-by: Richard Chapman <rchapman@hpccsystems.com>

system/jlib/jstring.cpp

@@ -2119,6 +2119,9 @@ inline StringBuffer &encodeJSONChar(StringBuffer &s, const char *&ch, unsigned &
             s.append('\\');
             s.append(next);
             break;
+        case '\0':
+            s.append("\\u0000");
+            break;
         default:
             if (next >= ' ' && next < 128)
                 s.append(next);