[rakudo] Make substr handle being given a negative start and length. Patch courtesy of Ronald Schmidt <ronaldxs@software-path.com>.
[rakudo] Make substr handle being given a negative start and length. Patch courtesy of Ronald Schmidt <ronaldxs@software-path.com>.

git-svn-id: ebc29296f9ec9cd27706eb0497c26fede0e190b2@34031 d31e2699-5ff4-0310-a27c-f18f2fbe73fe

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