Work around noexcept-in-type-system VS2017 bug

[dunhor]

Fixes #302

TL;DR - as I recall from vague understanding in the past - is that MSVC's "noexcept in the type system" update for C++17 "infected" pre-C++17 compilations, specifically for decltype. From what I recall when this initially started to impact us, decltype includes noexcept in the type, but that makes it impossible to assign/bind anything to such a function pointer since the noexcept gets dropped (as it should pre-C++17). VS2017 seems to be even more broken than this as allegedly even building with C++17 as the standard produces an error.

This change explicitly declares the function pointer type so that the issue will not be observed with the buggy version of the compiler. Ideally, we could just drop the type and use auto, but that's also a C++17 feature :/

[jonwis]

sad-panda.wav.tiff.mp4