Hotspot has specific sanity checks on Windows compiler and linker versions, MSVC_VER and LD_VER, and these need updating to recognise any new compiler.

Even if a compiler is not "officially supported", we want to be able to try builds with different compilers.

The build system's configure script now recognises alternate Visual Studio compilers on Windows, and can warn when a toolchain version is known to be problematic.

The specific sanity checks should be removed.