Work around a harmless assertion fault associated with

Work around a harmless assertion fault associated with
sqlite3VdbeMemAboutToChange() such that the detection of stale values
in registers is preserved in debugging builds, but we avoid a false-positive
assertion fault in cases involving a virtual table with a LIMIT clause
in an IN-operator loop.
dbsqlfuzz 3fd70d4ab4950acf1deb8f610a7a7c67cd38713b

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