buildroot

dropwatch: use new gettext logic

This commit switches to use the new gettext logic, which involves:

 - using TARGET_NLS_DEPENDENCIES instead of relying on binutils
   depending on gettext/host-gettext

 - using TARGET_NLS_LIBS to force linking against libintl

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>