Add test case for #942 std.parseYaml and block (pipe)

[pmorch]

std.parseYaml() doesn't handle this properly:

f1: |
  a
  b

A test case for issue #942

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[pmorch]

@googlebot I signed it!

[johnbartholomew]

Hi. Thanks for your contribution, and your patience!

I've rebased your commit (original commit b33649b1ee737ca22d03a960091d36ca5e169b3e, rebased commit 436c63ab81faae480689c3ae1d466af14e3b4136) and will merge it shortly.