- Avoid buffer overrun when too many readers.
- When remoinv reader ID, move one ID instead of all later IDs in array.
- assert(correct lock owner) before unlocking a write lock.

Expand usage struct with magic numbers and state info.
Add options "noreinit", "nosync", "nomem", "threadID".  Remove "dupinit".
Detect address changes.  Turn off thread ID tracking by default.

That way, realloc(qm->templates...) won't move the ldap_pvt_thread_rdwr_t data.

allow time/size limit errors as soon as some data is returned; don't divide by zero if no entries were found