Check for support of isnan infty etc.

[pgrete]

I noticed that some functionality may depend on proper results of isnan, infinity etc, which may, or may not, work as expected when the code basis is compiled with too much optimization (e.g., -ffast-math), which is, for example, the default in the original Athena++.
It may be worth to add a check at compile time, if the resulting binary works as expected with regard to these use cased and otherwise warn/fail/override.