Beta Release 1.15.16

Campaigns

Liberty
- S06: Enforce failure condition for allied team (issue #6019)

The South Guard
- S8b: Reduced difficulty

Tutorial
- S01: Don't let the first Quintain chase the player to a village (PR #5968)
- S01: Synchronise the choice of character dialog, so that replays don't get OOS (issue #5926)
- S01: Fix some glitches on HDPI displays (PR #6005)

Secrets of the Ancients
- Synchronise the walking corpse recruitment dialog, so that replays don't get OOS (issue #5334)

Under the Burning Suns
- S09: Reveal the boss of the scenario at the end of part 1 (issue #5540)

World Conquest
- Add campaign icons, campaign image and credits (PR #5958)
- Update to new mushroom terrain from the deprecated mushroom terrain (issue #5135, PR #5960)

Multiplayer

If an add-on needs to be installed on all players' devices but doesn't specify a min version, assume it needs the latest (issue #5004)

Terrain

Fix transition between snowy mountains and castles (issue #6016)

Translations

Updated translations: British English, Chinese (Traditional), Czech, Finnish, French, Indonesian, Italian, Polish, Portuguese (Brazil), Russian, Turkish

Units

Added and improved Naga animations (issue #5980, PR #6012)
Added Troll defense animations (PR #5964)

User interface

The names of the abilities used as specials appear in the attack prediction window with specials weapons
In the Load Game dialog, list directories from previous versions in decending order
Refined design of the Faction Select screen
Made the campaign selection on bigger on HDPI screens (PR #6013)

Miscellaneous and Bug Fixes

Added a timeout when connecting to the wesnothd server
Improved logging of deprecation messages, fixing duplication and missing timestamps (issue #5942)
Added `[era]` attributes to the schema
Added to wmllint an automatic update of four terrain-graphics macros
Removed wmllint's check for spaces in e-mail addresses
Standardised the date line of copyright statements, and updated them to 2021