Improve Range support

[jeffr-spire]

Fix the last-byte-pos value in Content-Range response
Return 416 Range Not Satisfiable if the range is beyond the file size

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The Content-range header being generated was invalid; the
last-byte-pos was equal to the complete-length. Especially notable was
that wget -c would fail on range requests.

#239 may be caused by this same issue.

From https://httpwg.org/specs/rfc7233.html#header.content-range:

A Content-Range field value is invalid if it contains a byte-range-resp that has a last-byte-pos value less than its first-byte-pos value, or a complete-length value less than or equal to its last-byte-pos value.