Missing `windmc.exe` Message Compiler

[Faisal Al-Humaimidi]

I was trying to build POCO C++ package using the LLVM MinGW toolchain, but was not able to complete the whole build without relying on MC.exe from VC toolchain. The latter tool is fine, but would love to have a self-contained MinGW toolchain that contains the windmc.exe tool, just like windrc.exe, ...etc.