[ANNOUNCE] NSPR 4.19 Release

The NSPR 4.19 release is now available.  The hg tag is
NSPR_4_19_RTM.  The source tar file can be downloaded from
https://ftp.mozilla.org/pub/mozilla.org/nspr/releases/v4.19/src/

NSPR 4.19 contains the following changes:
- changed order of shutdown cleanup to avoid a crash on Mac OSX
- build compatibility with Android NDK r16 and glibc 2.26

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=4.19