Broken links on website

[Ryan Plant]

Just a quick heads-up , https://gcc.gnu.org/install/binaries.html currently
has two broken links. "MinGW" leads to a dead site covered in
domain-parking ads, and the "mingw-w64" one 404s. I believe the current
links for those projects are https://osdn.net/projects/mingw/ and
https://www.mingw-w64.org/ respectively.