nls: delete six compose sequences that cannot be typed

None of the layouts in xkeyboard-config contain Ohook or Uhook or U+01D3 (U with caron) nor their lowercase forms, so these six sequences cannot be typed on any known keyboard.

(Also, the target characters of the sequences with hook and horn seem to occur only in Vietnamese, where the horn is part of the vowel and the hook is a tonal mark. All Vietnamese layouts in xkeyboard-config contain Ohorn and Uhorn, and then the five tonal marks as dead keys, dead_hook among them. It does not make sense to want to apply a horn to a vowel that already has a tonal mark, nor is it possible with the Vietnamese layouts.)

Signed-off-by: Benno Schulenberg bensberg@telfort.nl