missing gettimeofday.c in 0.8.19

[jaant]

scrypt-0.8.19.tar.gz does not include scrypt-windows-stubs/gettimeofday.c for some reason, causing the installation to fail on windows.

EDIT: probably because the MANIFEST.in only grabs *.h files from that dir.

[holgern]

Fixed in 0.8.20