jsoncpp: Suppress implicit-fallthrough warnings from GCC 7

GCC 7, when compiling with -Wimplicit-fallthrough=1 or higher, issues a warning which can be suppressed using a comment
that matches certain regular expressions. The comment change does just that: signal to GCC that the fall through is intentional.

Signed-off-by: GetAway <get-away@t-online.de>

lib/jsoncpp/jsoncpp.cpp

@@ -1454,8 +1454,7 @@ bool OurReader::readToken(Token& token) {
     token.type_ = tokenString;
     ok = readStringSingleQuote();
     break;
-    } // else continue
+    } // else fall through
-    /* is a break missing here? or is this correct? */
   case '/':
     token.type_ = tokenComment;
     ok = readComment();