[ANNOUNCE] NSPR 4.31 Release

[Kai Engert]

The NSPR 4.31 release is now available. The hg tag is
NSPR_4_31_RTM. The source tar file can be downloaded from
https://ftp.mozilla.org/pub/mozilla.org/nspr/releases/v4.31/src/

NSPR 4.31 contains the following change:
- avoid a race in multithreaded code

Additional details will be made available at a later time in
https://bugzilla.mozilla.org/show_bug.cgi?id=1686138

Thanks to all contributors to this release, in particular to Dana Keeler
who implemented the above improvement.

Kai