build: produce symbol map files on windows
This produces map files as part of the build on windows. The existence of these files enable profiling and tick-processing using the --prof command line. See: https://github.com/nodejs/io.js/pull/2090#issuecomment-124746673
Map files are documented here: https://msdn.microsoft.com/en-us/library/k7xkk3e2.aspx
R=@nodejs/build?