if tool mode needs to add structuralObjectClass, override any database setting (rationale: if configured w/ mirror mode and syncrepl, a master is also a shadow, but we need to be able to slapadd to a master (possibly with the correct SID; will deal with this later)

improve previous commit; fix ITS#5108 by letting both SID and RID be 0..4095, input/output in decimal, but consistently handled in hexadecimals within CSN

LBER_ALIGNED_BUFFER(OPERATION_BUFFER_SIZE), as discussed in ITS#4078.
Add a corresponding SyncOperationBuffer in overlays/syncprov.c.

Fixed line number in error messages to give the line number of the beginning
of the offending entry.

entry_schema_check() nows takes Operation instead of Backend as first
argument, allows it to check o_no_schema_check

bconfig.c and back-sql.