fix wcwidth of hangul combining (vowel/final) letters

fix wcwidth of hangul combining (vowel/final) letters

these characters combine onto a base character (initial) and therefore
need to have width 0. the original binary-search implementation of
wcwidth handled them correctly, but a regression was introduced in
commit 1b0ce9af6d2aa7b92edaf3e9c631cb635bae22bd by generating the new
tables from unicode without noticing that the classification logic in
use (unicode character category Mn/Me/Cf) was insufficient to catch
these characters.