Added MSWin64 build script

This is the build script for MSWin64 platform. You will need strawberry perl 64bit.
I tested it with version 5.18.2.2. If you don't have the 64bit version, get the zip version, move the 32bit folder to the side and extract the 64bit version into c:\strawberry. Run "relocation.pl.bat" and "update_env.pl.bat" to finish installing it. Install all dependencies for biber and install it (Encode::JIS2K refused to install because it could not find enc2xs: fix it by providing a fixed path for $enc2xs variable in Makefile.pl and then manually installing it). I also ran upx with option --lzma on the entire perl folder recursively to get the biber executable file size down. This should be done before installing PAR::Packer, because it seems to cache some libraries upon install which cannot be packed afterwards. Last, make sure the paths in the biber build script are correct and run it. My executable ended up being 14.7 MB big.

To get the 32bit perl version back, simply move it back to the original folder and run "relocation.pl.bat" and "update_env.pl.bat".