GH-2864: Fix algebra function name for the hash functions.

[afs]

GitHub issue resolved #2864

The algebra operator symbol should be lower case.
Print in SPARQL is overridden to be upper case as it has been for a long time.

Some reformatting in-passing.

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• Tests are included
• Key commit messages start with the issue number (GH-xxxx)

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[rvesse]

Change looks good

Do we want some test cases that cover the scenario that prompted the bug report?

Given your analysis that this has existed basically forever in the code base that strongly implies there are no pre-existing test cases that expose this bug

[afs]

It's a display bug in printing algebra. The execution of queries isn't affected which presumably is why is hasn't come to light.

With the exception of qparse, I can't think of any non-development case of writing algebra derived from query syntax in a way that is going to be read in again. Writing is mainly for development, and parsing algebra for testing isn't based on the output of query syntax. Some of this "grew" in stages over an extended (pre-ASF) period of time.

[afs]

@rvesse - please use "rebase and merge".

The choice should be sticky by repo and not affect your choice elsewhere.