Correctly handle CJK/double width characters.

Some CJK characters take more than more column on the terminal, so should use wcswidth to calculate the screen width. Also fixed potential buffer overflow in calls to swprintf.

Fix the date in rover.1

Silences the following warning from mandoc(1) man -Tlint rover cannot parse date, using it verbatim (mdoc, man) The date given in a Dd or TH macro does not follow the conventional format. man: rover.1.gz:1:13: WARNING: cannot parse date, using it verbatim: rover\-1.0.0 https://man.openbsd.org/mandoc.1

VISUAL is useed on many systems these days without EDITOR being set, see the manual pages for various shells or other documentation. This patch makes rover respect VISUAL being set in the environment and prefer it to EDITOR.

Use 'rm -f' in Makefile