Make network buildable on all MSYS flavours

The first commit simply refreshes GNU config (current is 8 years old).

The second removes wspiapi.h references which breaks things when the package is built with mingw-w64-based GHC distributions (it is an official 64-bit GHC, and my private 32-bit GHC port, which I want to propose to replace current mingw-based 32-bit GHC when I have time). Wspiapi only exists on pre-XP windows' which aren't supported by recent GHC/network anyway AFAIUI.

Third makes configure recognize 'mingw64' os part of a configure triplet. It is current preferred configuration when building things with 64-bit windows GHC under MSYS2.