package/minetest: bump to version 5.0.0

package/minetest: bump to version 5.0.0

"5.0.0 is a breaking release and not compatible to the 0.4 series", so
update minetest-game package in the same commit.

Update GCC dependency to 4.9+.

Use LICENSE.txt as license file instead of the README.md.

Update license files hash for minetest-game after checking what's changed.
Add new license files for minetest-game.

https://forum.minetest.net/viewtopic.php?t=22278

Signed-off-by: Romain Naour <romain.naour@gmail.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>