This is a follow-up to JDK-8353480

We have:

  static char* map_memory(int fd, const char* file_name, size_t file_offset,
                           char *addr, size_t bytes, bool read_only = false,
                           bool allow_exec = false, MemTag mem_tag = mtNone);


Suggestion from Stefan:
- drop default values for allow_exec and mem_tag
- reverse the order of allow_exec and mem_tag