Apply nodame's small fixes to vspipe

git-svn-id: http://vapoursynth.googlecode.com/svn/trunk@512 f9120d27-2007-6f97-8312-0f4ebfa7710f
Fix previous commit

git-svn-id: http://vapoursynth.googlecode.com/svn/trunk@513 f9120d27-2007-6f97-8312-0f4ebfa7710f
Merge branch 'master' into cuda