CMake: Fix #149.
Check for the definition of `_MSC_VER`, rather than its value.
Merge pull request #153 from pqu/_msc_ver-def

Check for the definition of `_MSC_VER`, rather than its value.
Merge pull request #152 from pqu/cmake-fix

CMake: Fix #149.
Fix 32-bit build.
Merge branch 'master' of github.com:kentonv/capnproto
Refactor UnixEventPort interface to be edge-triggering-friendly.