boinc: 7.4.14 -> 7.4.42

As it turns out BOINC moved their git repository to Github sometime
shortly after the first update to this derivation. Their wiki change
makes this quite clear:
https://boinc.berkeley.edu/trac/wiki/SourceCodeGit?action=diff&version=54

Slight refactor and the changelog for this release can be found here:
https://boinc.berkeley.edu/trac/wiki/VersionHistory

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