package/minetest{-game}: bump to version 5.5.1

Release announcement:
5.5.0: https://forum.minetest.net/viewtopic.php?f=18&t=27754
5.1.1: https://forum.minetest.net/viewtopic.php?p=410344#p410344

Back in 2021, the minetest project forked the irrlicht library due to
lack of upstream release [1]. But the irrlicht upstream project is not
really halted since a stable 1.8.5 version has been released [2] and
there is still svn activity.

But the Mintest fork (called irrlichtMt) is attractive since:
  - It use a CMake build system instead of hand written makefiles [3]
  - Bundled libraries has been removed [4] [5]
  - It allows to remove the NEON support workaround for bundled libpng
  - It use git as VCS
  - Improve the licensing information

This irrlichtmt is required since mintest 5.5.0 version but contains
several changes specific to Minetest, so add irrlichtmt as additional
sources using EXTRA_DOWNLOADS.

minetest:
- Add zstd dependency for MapBlock compression [6]
- Freetype is now a build requirement for mintest client [7]
- gcc >= 5.x is now required [8]
- remove upstream patch [9]

minetest-game:
- Add new license files:
    mods/keys/license.txt
    mods/mtg_craftguide/license.txt
    mods/weather/license.txt

[1] https://forum.minetest.net/viewtopic.php?p=393565
[2] https://irrlicht.sourceforge.io/forum/viewtopic.php?f=2&t=52775
[3] https://github.com/minetest/irrlicht/commit/6ce98dce7789c96dded00fabfe409356f954edfe
[4] https://github.com/minetest/irrlicht/commit/67f1402410a5b90f11c2a2bd69ba5d73eb6e943a
[5] https://github.com/minetest/irrlicht/commit/264f8b72c1dce7c209ac8daaf0484aa3af7740b7
[6] https://github.com/minetest/minetest/commit/d1624a552151bcb152b7abf63df6501b63458d78
[7] https://github.com/minetest/minetest/commit/76dbd0d2d04712dcad4f7c6afecb97fa8d662d6d
[8] https://github.com/minetest/minetest/commit/a90b2a4d4f38e92b4016d9ac86e001398be729e7
[9] https://github.com/minetest/minetest/commit/7c2826cbc0f36027d4a9781f433150d1c5d0d03f



Signed-off-by: Romain Naour <romain.naour@gmail.com>
[Arnout: simplify symlink command]
Signed-off-by: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be>