pgsql: Add variant regression file to support BSDen that underflow to

Log Message:
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Add variant regression file to support BSDen that underflow to plus zero instead
of minus zero. Per Andrew Dunstan.

Added Files:
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pgsql/src/test/regress/expected:
float8-small-is-zero_1.out (r1.1)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/test/regress/expected/float8-small-is-zero_1.out?rev=1.1&content-type=text/x-cvsweb-markup)