Update ANNOUNCE to 2.3

Update ANNOUNCE for 2.2.1

Add MinGW CI

Copy ANNOUNCE for 2.1 release.

Fix long vs size_t error on Windows.

On win64, long is 32 bits, not 64 bits as it is everywhere else.

Fix accidentally inverted preprocessor directive.

Added 1.8.1 release announcement.

Fix copy and paste error in release announcement.