nls: Allow all letters with a caron to be composed also with v.

It was strange that the accented letters Ž and ž can be composed with sequences that start with "v" ("v Z" and "v z"), but not Č and č and Š and š (and other letters with a caron). For these letters, compose sequences that start with a "c" had to be used, which was frustrating because it is hard to remember that "c" stands for "caron", AND the graphically more obvious "v" is right next to it.

(Unfortunately, the sequence "v l" is already taken for vertical line. Maybe the compose sequences for vertical line could be reduced to just "V L" and "L V"?)

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