scaladoc continues with bad option

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A bad cli option should hard exit. Instead the bad option is interpreted as a source file containing documentable content.

11:16 $ ./scaladoc -h
scaladoc error: bad option: '-h'
  scaladoc -help  gives more information
error: source file '-h' could not be found
model contains 1 documentable templates
two errors found

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Imported From: https://issues.scala-lang.org/browse/SI-9793?orig=1 Reporter: @janekdb Affected Versions: 2.12.0-M4

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Chase Long (chasel_long) said: I submitted a PR for this: https://github.com/scala/scala/pull/5215

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@SethTisue said: The PR was closed for inactivity. Would someone else like to pick it up...?