json: Optimize memory usage by not collecting string values

When a string is not used as an object property the parser doesn't
need to know its value.  Not collecting it into memory lowers memory
consumption and avoids high memory consumption with huge string values.

tagmanager/ctags/json.c

@@ -138,7 +138,8 @@ static boolean isIdentChar (int c)
 	return (isalnum (c) || c == '+' || c == '-' || c == '.');
 }
 
-static void readToken (tokenInfo *const token)
+static void readTokenFull (tokenInfo *const token,
+						   boolean includeStringRepr)
 {
 	int c;
 
@@ -178,7 +179,8 @@ static void readToken (tokenInfo *const token)
 					break; /* break on invalid, unescaped, control characters */
 				else if (c == '"' || c == EOF)
 					break;
-				vStringPut (token->string, c);
+				if (includeStringRepr)
+					vStringPut (token->string, c);
 			}
 			vStringTerminate (token->string);
 			break;
@@ -209,6 +211,8 @@ static void readToken (tokenInfo *const token)
 	}
 }
 
+#define readToken(t) (readTokenFull ((t), FALSE))
+
 static void pushScope (tokenInfo *const token,
 					   const tokenInfo *const parent,
 					   const jsonKind parentKind)
@@ -287,7 +291,7 @@ static void parseValue (tokenInfo *const token)
 
 		do
 		{
-			readToken (token);
+			readTokenFull (token, TRUE);
 			if (token->type == TOKEN_STRING)
 			{
 				jsonKind tagKind = TAG_NULL; /* default in case of invalid value */