Proof-of-concept grammar rules to parse Google-style "pipe" syntax for SQL,

Proof-of-concept grammar rules to parse Google-style "pipe" syntax for SQL,
without the ghastly "|>" operator.  The grammar rules are not connected to
working code.  They just parse the syntax.  Pipelines that begin with an
ordinary SELECT statement must have the keyword "INTO" (rather than the
"|>" operator) separating the SELECT from the start of the pipeline, to
avoid syntactic and semantic ambiguity.

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