New version 1.4

- Add trackig of freed context and assert on using a context after it has been
  freed.
- Windows x64 support and fixes.
- Switch to using our own version of xdr_int64() since the one in libtirpc
  crashes on some platforms.
- Fix memory leak in an error path for addrinfo.
- Fix bug dereferencing a null pointer in the mount callback on error.