Make flightmode, switch and system file names case insensitive.
Update DONATIONS.txt
Fixes #967
Merge pull request #966 from projectkk2glider/sound_filenames_case_insensitive

Make flightmode, switch and system file names case insensitive
strcasecmp used rather than strcmpi
Fixes #965
Fixes #968
German Companion translation updated by Hrenz
Updated German translation of OpenTX by Hrenz
Fixes #934
Fixes #973
Fixes #974
GVAR popups only for Taranis...
Fixed many memory leaks
* One more leak fixed.
* debug print removed
Update DONATIONS.txt
* Added space between channels in mixers tab, amount defined by MIX_ROW_HEIGHT_INCREASE
* Added highlighting of selected channel when used as source in other channels (Ctrl+T or context menu->Toogle highlight)
* Added leading zero to channel name for ch_number < 10 (better alignment for CH1 to CH9)
Fix "Move up a mix will not move higher than the current topmost line entry"
Fixes #977
Better fix for #977