[ANNOUNCE] NSPR 4.20 Release

[Kai Engert]

The NSPR 4.20 release is now available. The hg tag is
NSPR_4_20_RTM. The source tar file can be downloaded from
https://ftp.mozilla.org/pub/mozilla.org/nspr/releases/v4.20/src/

NSPR 4.20 contains the following changes:
- Added support for the RISC-V 64-bit target.
- Added support for aarch64 Windows.
- Added support for abstract socket addresses on Linux and Android.
- Fixed a FreeBSD build issue.
- ASAN poisoning functions on Windows no longer use the dllimport
attribute.

For details, please refer to the list of related bugs:
https://bugzilla.mozilla.org/buglist.cgi?resolution=FIXED&query_format=advanced&product=NSPR&target_milestone=4.20

Thanks to all contributors to this release.
Kai