Wrapper around MSVC cl.exe for autoconf.

I've written a wrapper around MSVC cl.exe for autoconf (see
https://wiki.documentfoundation.org/Development/Gsoc/Ideas#Gcc_like_wrapper_for_MSC_on_cygwin_and_autotools_compatibility
).

The goal of the wrapper is to remove all the custom MSVC logic from the
ExternalProject makefiles and let the packages just use autoconf.

I've uploaded the gcc-wrapper patch to gerrit as well as two example
implementations.

The code was rather quickly hacked together so it may still be buggy.

Is this something that should be integrated into libreoffice?

Thanks,

Peter