C99 and GMP

[Martin Storsjö]

On Wed, 4 Apr 2018, Torbjörn Granlund wrote:

> I'd suggest to make a 6.2 release of pretty much what we have today.

Before releasing, I'd appreciate if someone could have a look at the 
configure patch for windows/aarch64. It shouldn't have any effect on any 
other, existing setup, and matches what already is done for x86_64 (in 
using "long long" for 64 bit integers).

// Martin