Added corrections to re-enable reciprocal test in math_brute_force suite for relaxed math mode

[shajder]

fixes #2145

As suggested by @svenvh reciprocal has different precision requirements than divide. This PR introduces special path for reciprocal for binar_float_operator to test reciprocal with relaxed math. If this PR will get approvals, invalidate PR #2162

[bashbaug]

Possibly dumb question: why are we introducing a special path through binary_operator_float to test reciprocal? Reciprocal is a unary operation, not a binary operation...

[shajder]

Possibly dumb question: why are we introducing a special path through binary_operator_float to test reciprocal? Reciprocal is a unary operation, not a binary operation...

Yep, good point. I went that way just because I wasn't able to choose a better spot. There is no unary float operator, right? To create one I would have to duplicate a lot of code. Any other clues?

[svenvh]

Possibly dumb question: why are we introducing a special path through binary_operator_float to test reciprocal? Reciprocal is a unary operation, not a binary operation...

Yep, good point. I went that way just because I wasn't able to choose a better spot. There is no unary float operator, right? To create one I would have to duplicate a lot of code. Any other clues?

Treating reciprocal as a binary operator with its first argument being the constant 1 seems the least worst solution for now. I'm in the process of reducing code duplication in the math bruteforce suite, so eventually we may be able to move it into its own place. But for now I'm okay with @shajder's chosen solution.