Corrected gmxcheck output for Gromos96 bonds.

There was a small output bug since Gromos96 bonds are modified to have
the reference value stored as (b0)^2 rather than just b0.

Fixes #1109.

Change-Id: Ie4516515f7cacb35d262c2059b5e461962340fec
Merge "Corrected gmxcheck output for Gromos96 bonds." into release-4-6