* provide flags for minetest release as adventuretest.<flag> for
example to check 5.0 just `if adventuiretest.is_50 then` but
such mod must depends on default or adventuretest mods
* thos also add a pseudo check to 4.0.17 that is 0.4.17.2 and go
the 0.4.18 version from sfan is not take into consideration cos
provides so many things about 5.0 that must not be in such release.