Bugfix: UTF-8 functions fail to properly handle ASCII.

Bugfix: UTF-8 functions fail to properly handle ASCII.

This seems to be a problem where there are two ways of processing ASCII detection of UTF-8 code.

The macro_f_utf_byte_width() will return the width of 1 for ASCII.
The macro_f_utf_byte_width_is() will return a width of 0 for ASCII.

The affected code is assuming a width of 0, but some functions send a width of 1 for ASCII.
These are private functions, so it is relatively safe to just allow both.

Change the behavior to accept both 0 and 1 and treat them as ASCII.

Update comment about Unicode 12.1, setting it to 14.0.