Previously vimwiki#tbl#get_cells() would act on `line` as a normal
string (i.e. using `[idx]` and strpart()). This breaks when the column
separator (s:s_rep() or rxTableSep) is a multibyte character like the
vertical box drawing character │. In that case the separator is never
found and only one empty cell is returned. This also affects
vimwiki#tbl#format() which in turn clears the whole table each time the
insert mode is left.
Fix this issue by initially splitting the line into a list of the
characters. Getting the elements with `[idx]` now returns each character
instead of a byte. In addition len() is used in place of strlen() as
well as slicing together with join() instead of strpart().
Fixes: #1297 ("Table formatting breaks on multibyte separator")
Julian Prein
c5b7f7e76f
