Additional bug fix after openCL merge

- typo's and missing variable declaration in openCL processing
- changed OpenHiFUS.pyw to only replot every second captured frame
Bipolar "AcquireBuffers"

Previously Only returned positive values. Fixed to return negative or positive values.
Merge pull request #6 from mcleung/patch-1

Bipolar "AcquireBuffers"
Merge pull request #1 from j-leadbetter/master

Update to new