RFR: Unstuck version

[Jiří Vaněk]

See https://github.com/openjdk/asmtools/pull/36 for background

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Commit messages:
 - reworked stdin read to be initiated by -
 - Stream based inputs are now drained once needed, not during construction
 - Properly exiting after verson is printed

Changes: https://git.openjdk.org/asmtools/pull/40/files
 Webrev: https://webrevs.openjdk.org/?repo=asmtools&pr=40&range=00
  Stats: 159 lines in 15 files changed: 123 ins; 4 del; 32 mod
  Patch: https://git.openjdk.org/asmtools/pull/40.diff
  Fetch: git fetch https://git.openjdk.org/asmtools pull/40/head:pull/40

PR: https://git.openjdk.org/asmtools/pull/40