distinguish the quote character from quoted symbols

tokenize.c

@@ -272,10 +272,10 @@ match_symbol(source_t source,
     return false;
   }
   i++;
-  while (!isspace(source[i]) && i <= length) {
+  while (!isspace(source[i]) && i < length) {
     i++;
   }
-  if (i == begin) {
+  if (i == begin+1) { /* if we did not increment i more than once (before the loop) */
     return false;
   }
   return i;