Allow more tolerance in pair inverse detection

[doug-walker]

The optimizer will remove pairs of adjacent ops that are inverses of each other. However, the comparison is probably more strict than it needs to be. For example these ops are not removed:

        <FixedFunction direction=inverse, style=REC2100_Surround, params=0.833333333333333>
        <FixedFunction direction=forward, style=REC2100_Surround, params=0.8333333333333334>

This is especially problematic since the CTF writer will output the param from line 2 as the value from line 1.

The tolerance for making these comparisons should be increased slightly.