Prevent right-shift by 32

Fixes #93.
8 jobs for master in 2 minutes and 15 seconds (queued for 2 seconds)
Status Name Job ID Coverage
  Build
passed build-debian #5308
debian amd64

00:00:31

passed build-debian-aarch64 #5312
aarch64 debian

00:01:40

passed build-debian-aarch64-clang-5 #5313
aarch64 clang5 debian

00:01:17

passed build-debian-static #5309
debian amd64

00:00:32

passed build-debian-werror #5315
aarch64 debian

00:00:57

passed build-macos #5314
macos

00:00:23

passed build-win32 #5310
win32

00:00:28

passed build-win64 #5311
win64

00:00:32