Make inequalities behave the same as their operators when infinity is involved.

Previously, Lt(x, oo) would not evaluate, while x < oo would return True.
Tests for this (marked XFAIL) were added in pull request #7783.  Now, all
inequality classes (Lt, etc.) will harness the same code behind the operators
(<, etc.) whenever positive or negative infinities are involved, guaranteeing
that the two produce identical results.

Note that the test in question has not had its XFAIL removed, as pi > x does
not yet behave the same as Gt(pi, x).  Once this is corrected too, the test
will pass.
The test isn't scrapped, per se.  The for loop below includes that particular combination, and it was only at the top to highlight that it fails and make it fail fast.  If it no longer fails fast, there's no reason to test that an extra time at the start.

But of course all of this is moot since Travis shows tons of other errors introduced by this change, so I have to give it a much closer look.