If the -tag list definition didn't have a -width modifier,
the first .It call was supposed to set the width depending
on the first argument type; if it is a macro name, use the
macro's width value; otherwise, use width value of `No'.
The following two lists should produce identical output:
.Bl -tag -width Er -compact
.It Er EINVAL
invalid argument
.El
.Bl -tag -compact
.It Er EINVAL
invalid argument
.El
If the outermost -tag list definition did't have a -width
modifier, the .It elements of inner lists might not work
(producing a list where each successive element `walks' to
the right).
Example:
.Bl -tag -compact
.It outer
.It outer
.Bl -tag -compact
.It inner
.It inner
.El
.It outer
.It outer
.El
Ported from: mdocNG
abec56f578