is_value...() functions

Check the variable type
Returns true if the variable type is the expected one
Thread-safe functions.

success value_is_string(var);
success value_is_long(var);
success value_is_float(var);
success value_is_object(var);
success value_is_func(var);
success value_is_pvoid(var);
success value_is_int64(var);