ignoring control characters in character width

[Patrice Dumas]

Hello,

Currently, when counting the width of a line of character, we count
control characters that are also spaces as having a width of 1.  I think
that it is not good, as control characters either should not have a
width, for end of line, form feed, carriage return, or have a width that
is not well defined for vertical and horizontal tab.  I suggest to
consider all the control characters as having a width of 0.  This will
be consistent with libunistring u8_strwidth, which I intend to use in C
code equivalent to perl code.

Thoughts?

-- 
Pat