maint: adjust copyright notices in *.in files to be consistent

maint: adjust copyright notices in *.in files to be consistent

The copyright year ranges in *.in files were not being updated,
because of a missing ", Inc." suffix.  Add that, run
run "make udpate-copyright", and ensure 2010..2015 year
ranges are covered.
* gunzip.in: Update copyright notice and year ranges.
* gzexe.in: Likewise.
* zcat.in: Likewise.
* zdiff.in: Likewise.
* zforce.in: Likewise.
* zgrep.in: Likewise.
* zless.in: Likewise.
* zmore.in: Likewise.
* znew.in: Likewise.