calc 2.12.6.6 release

The following are the changes in this release:

For historical purposes, in lucas.cal, gen_v1(1, n) always returns 4.

Fixed some compiler warnings, thanks to a report by Mike
<michael dot d dot ince at gmail dot com>.

Added work around for a gcc warning bug, thanks to a report by Mike
<michael dot d dot ince at gmail dot com>.