Merge branch 'tb/unicode-6.3-zero-width'

Update the logic to compute the display width needed for utf8 strings and allow us to more easily maintain the tables used in that logic. We may want to let the users choose if codepoints with ambiguous widths are treated as a double or single width in a follow-up patch. * tb/unicode-6.3-zero-width: utf8: make it easier to auto-update git_wcwidth() utf8.c: use a table for double_width