Add STRICT to some C functions created by the regression tests.

Add STRICT to some C functions created by the regression tests.

These functions readily crash when passed a NULL input value.  The tests
themselves do not pass NULL values to them; but when the regression
database is used as a basis for fuzz testing, they cause a lot of noise.
Also, if someone were to leave a regression database lying about in a
production installation, these would create a minor security hazard.

Andreas Seltenreich