Deprecating fromIntegral

[Henning Thielemann]

On Fri, 22 Sep 2017, Evan Laforge wrote:

> I've had similar bugs due to sloppy haskell -> C FFI conversions so I'm 
> sympathetic to the idea.  It's just a blanket deprecation on 
> fromIntegral seems like a broad brush.

I assume that conversion causes problems depending on the architecture. 
E.g. Int -> CInt might be a lossless conversion on a 32-bit architecture 
and lossy on 64-bit.