Bump luvit to latest and enable 64bit Windows versions

* bump luvit for latest libuv
* enable x64 native on Windows
* use relative paths to make the bundle list easier to read
    and less messy in the MSVS IDE.
* supports Windows vista and above only
* more .gitignore
* remove obsolete calls to activateSignalHandler
* carry over init code from luvit for process metatable and signals