Merging desktop icon settings

applications-math.desktop and setxkbmap-gadget.desktop are installed
on Desktop when LXDE starts up.
Adding a boot-time hook for kseg language settings

The "Language = kseg_en.qm" line in ~/.kseg will be overwritten according to locale.
Adding l10n entries to boot menu

This hook overwrites binary/BOOTLOADER/live.cfg. It adds language menu
entries if task-LANGUAGE's are installed.