patch 9.1.0038: Unnecessary loop in getvcol()

patch 9.1.0038: Unnecessary loop in getvcol()

Problem:  Unnecessary loop in getvcol().
Solution: Compare next char position with pos->col directly.
          (zeertzjq)

The loop below already handles end of line before checking for posptr,
and the next char is after pos->col whether pos->col is at the start or
in the middle of the char in question, so neither the NUL check nor the
mb_head_off() are needed when comparing the position of the next char
with pos->col directly.

closes: #13878

Signed-off-by: zeertzjq <zeertzjq@outlook.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>