* Make __float128 a floating point type.
Allows float128 to be used in non gnu mode.
Enable some tests for non-gnu mode.
Fixes https://github.com/boostorg/multiprecision/issues/569.
Also:
* Remove msvc-14.0 testing as no longer supported.
* correct float128_snips.cpp
* Run specfun tests on github rather than CircleCI as the latter runs out of resources.
