dbUnitTest::testdbRecordPtr() is easy to mis-use

[Andrew Johnson]

There can be a mis-match between the record type expected and the type of the record returned, but a typical use of testdbRecordPtr() will cast the pointer to the expected type with no warnings produced if it's wrong, and any test code that accesses a record-specific field will likely be pointing at the wrong address.

It should be possible to define a new macro in dbUnitTest.h and an associated helper function that takes the expected record type as an argument and checks that the type returned matches the one expected, returning a pointer that is already cast to the expected type. It should call testAbort() if the wrong record type is found.