minGW 'make check' errors

[Rik]

11/3/13

This bug report details some errors which apparently only appear on the
minGW system (https://savannah.gnu.org/bugs/?32036).

Specifically, it seems that log2 (Inf) = Inf on all other platforms and NaN
on minGW.  Given that minGW is linking against Windows math libraries, and
I don't see Microsoft changing anytime soon, I think we should make
exceptions for these two tests when minGW is detected.  After all,
reporting them as failures isn't going to change Octave's code (log2(Inf)
should be Inf), nor is it going to be a spur to Microsoft to change their
libraries.  Thus, the point of a failing test being a prod to get something
fixed is rendered moot.

--Rik