id2entry: when an error occurs attempting to insert fetched
entry into cache, check to see if entry was added by another
thread. If so, return the entry added by the other thread.
The concurrency tests now run without the dreaded "no such object"
error messages!
Integration into ./configure ( --enable-bdb2 ).
Adaptation of the test-suite ( 'make' -> ldbm; 'make bdb2-local' -> bdb2 ).
Minor fixes in slapd/libldbm.
BEWARE: the backend will be compiled.
the backend will NOT be invoked, yet.
the backend CANNOT be invoked, yet, because it is NOT yet
integrated into the new initialization/startup environment
of the slapd server.