Fix tag width calculation for multi-column chars
* lisp/org.el (org-align-tags-here): Fix tag width calculation for
multi-column chars.
Some characters have multiple column width. Calculating string width
with points gives a wrong value than actual display width. Use
`string-width' instead.
Here is an ECM for this problem. `M-x org-update-statistics-cookies` or
`C-c #` on bar moves the tag on the headline.
* foo [0/0] :abc:
** child
* bar [0/0] :日本語:
** child
12345678901234567890123456789012345678901234567890123456789012345678901234567890
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