Here are patches needed for a Wimdow 64 build done with msvc2015 : https://github.com/syntheticpp/lyx/commits/msvc15-amd64
Most changes because long is only 32bit on Windows. http://www.viva64.com/en/t/0012/ Having a look at the tabe it seems nobody toke the coutage to make int 64 bit wide on 64 bit systems ;-)
