The returned record numbers don't care about deleted records. You should read each and any
record and determine yourself whether the record is deleted or not (check the record's
leading byte, being 0x20 a normal record, and 0x2A a deleted
record).
See the example below to see how to use it all. You might say that this set of routines
is very low level, but C++ itself is low level, too...
Important note: if the NTX exists but FFNtxOpen fails then wait a second and
retry (this could happen if the NTX is locked by some other user).