Helmert transformation

Using my rudimentary knowledge of C I have implemented the helmert transformation and some other functions to make it useful.

This may be completely the wrong way to do it and I am happy to change any of it but just thought it would be good to get the functions in there.

I based the calculations on the spreadsheet www.ordnancesurvey.co.uk/oswebsite/gps/docs/ProjectionandTransformationCalculations.xls which seemed to be a pretty accurate source.