Remove checks for Perl 5.6; adjust tests; bump version number.

Remove checks for Perl 5.6; adjust tests; bump version number.

Patch contributed by Sébastien Aperghis-Tramoni

For: RT #114770.

# Please enter the commit message for your changes. Lines starting
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# On branch blead
# Your branch is ahead of 'origin/blead' by 1 commit.
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# Changes to be committed:
#   (use "git reset HEAD^1 <file>..." to unstage)
#
#	modified:   dist/constant/lib/constant.pm
#	modified:   dist/constant/t/constant.t
#