Rules for MinGW on MacPorts

[AMDmi3]

From repology/repology-updater#383 by @mojca:

The MinGW packages for MacPorts are split in a weird way. There's mingw-w64 which is some kind of a meta-package and is at the same version as *-w64-mingw32-crt, *-w64-mingw32-headers (and soon *-w64-mingw32-winpthreads).

Then *-w64-mingw32-gcc is basically gcc cross-compiler. And *-w64-mingw32-binutils is basically binutils for cross-compiler. I don't know against which packages these are supposed to be compared and I'm not sure how to write the rules for such a split, but it would be nice to correct this.

(Plus there's a bunch of abandonware i386-mingw32-*.)

[AMDmi3]

I'm a bit hesitant regarding these for now. At the one hand, they should be merged with corresponding gcc/binutils along with all cross-** packages. At the other hand, these are still useful as separate metapackages, otherwise the information on which repos have mingw support is hidden. We could both, but it's not possible to attach a package to multiple metapackages yet (see #163). I guess I'll leave this issue for later.