(ITS#3958) addition of "undefined" attribute descriptions should be mutex-protected

[ando@sys-net.it]

Full_Name: Pierangelo Masarati
Version: HEAD/re23/re22
OS: Linux
URL: ftp://ftp.openldap.org/incoming/
Submission from: (NULL) (81.74.43.82)
Submitted by: ando


"undefined" attribute descriptions are generated run-time and appended to the
list of attribute descriptions of the "undefined" attribute type.  This
operation should be mutex-protected to aviod the (rare) eventuality of
concurrency issues.  Same for "undefined" objectClasses.

A fix is coming.