ncal: always generate full lines to enable today hilight in year view

ncal: always generate full lines to enable today hilight in year view

Ncal would only fill lines up to the last day in a month and use a printf
padding later to align all output nicely (when using year view).  This
breaks when using a hilight, because the ANSI sequences consume additional
characters which are of zero print width.  Instead of letting printf do
the padding, generate padded lines ourselves.

Also avoid code duplication in the hilight code and switch on hilighting
for the year view.