Save one iteration in parse_number

src/test.cpp

@@ -461,6 +461,8 @@ private:
       return false;
     }
     callbacks->on_begin_number(data);
+    ++buf;
+    --len;
     for (;;) {
       if ('0' <= *buf && *buf <= '9') {
         ++buf;
@@ -839,6 +841,7 @@ private:
 };
 
 const std::string json = R"({
+    "a number": 12345,
     "glossary": {
         "title": "example glossary",
 		"GlossDiv": {