add mingw64 build

[vicentebolea]

This add mingw-w64 windows build.

Feel free to push to this branch to resolve this

[eisenhauer]

@vicentebolea If you can resolve the conflicts for the CI setup here, I'll poke at this gradually. There are a lot of errors in a lot of different places, so my plan would be to test fixes for each issue here, and when a fix works, roll it out of here, put it in master and then rebase this on master. It won't be a fast process, but there's a lot of things in a lot of places so maybe piece-wise is the way to go. There's also an error in KWsys, so you might take a look at that too. Thanks!

[vicentebolea]

@eisenhauer conflicts resolved

[eisenhauer]

@vicentebolea I'll check when CDash comes back up, but I believe that the latest set of things merged to ADIOS master address all the Mingw compiler issues in ADIOS and the GTKorvo upstream packages. The remaining issue in KWSYS and the compiler errors when #including threads are something else that you may be best positioned to sort.