On some systems, there is a /usr/bin/lrelease wrapper even if the real
lrelease program is not installed. So let's try to execute lrelease
after it has been found by find_program to see if it is really working.
If a translation file exists in a "translations" directory located in
the same directory as the binary, it is used in priority (this can be
useful when working on translations as you don't have to recompile the
whole program all the time), and if no such file is found the embedded
translation file is used (if it exists).
Changed the wording from "from 0 to maximum available" to "from 2 to maximum available".
May I also suggest putting in a number rather than "maximum available" and also clarifying that mixin = 0 is still allowed if the user has unmixable outputs (dust), which he wants to "undust" using sweep_unmixable (comment from dEBRUYNE-1 ).
