Make validation mode parameter explicit in DATA_CHECK macros [blocks #3287]

[danpoe]

As requested by @tautschnig in a comment to an earlier PR, this makes the validation mode an explicit parameter of the DATA_CHECK() macros.

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[allredj]

✔️
Passed Diffblue compatibility checks (cbmc commit: 76f0ec7).
Build URL: https://travis-ci.com/diffblue/test-gen/builds/93038258

[xbauch]

Looks good.

[NlightNFotis]

LGTM. This is well done, prefer the explicit passing of it around to the assumption that a vm variable should be in scope.

[tautschnig]

Thank you!