TranslateDesktop: Use -a switch in grep commands
TranslateDesktop: Use -a switch in grep commands

As of grep v2.23 some translation files are considered as binary (maybe because of some locale settings)
and then the created .desktop file is malformed. So we force the grep to handle all provided input
files as text.

closes lxde/lxqt#957

lxde/liblxqt,ThomasVie/liblxqt,pmattern/liblxqt,pmattern/liblxqt,ThomasVie/liblxqt,lxde/liblxqt