Msys2 based Windows Installer testing (freeciv-3.1)

[cazfi]

New freeciv master msys2 build from sources of 05-Jan-21 (3.0.93.1-dev-210105), commit '3466068fa5', available at http://files.freeciv.org/packages/windo ... snapshots/

- Built against msys2 environment 201212

[cazfi]

New freeciv master msys2 build from sources of 03-Feb-21 (3.0.93.2-dev-210203), commit '0a32b72a97', available at http://files.freeciv.org/packages/windo ... snapshots/
This is last build before S3_1 gets branched from master, and so the last common ancestor for future 3.1 (from S3_1) and 3.2 (from master) builds.

- Built against msys2 environment 201212

[cazfi]

New freeciv S3_1 msys2 build from sources of 05-Mar-21 (3.0.93.4-alpha-210305), commit '75a00967d5', available at http://files.freeciv.org/packages/windo ... snapshots/

- Built against msys2 environment 210226