[msvc] Refreshed .def files (needed for SGen to build)
[msvc] Add missing sgen source files to libmonoruntime.vcxproj
[msvc] Add _SGen Configurations to {eglib,libgc,genmdesc}.vcxproj

These configurations are needed to build a Debug_SGen version of mono.vcxproj, which is needed to build mono-sgen.exe
Merge pull request #1423 from directhex/sgen_on_msvc

[msvc] Get sgen building on MSVC