Some LF demod are still expecting ProxmarkII half-sampled data

[GoogleCodeExporter]

At least vchdemod and flexdemod, others should be reviewed as well.
Short term fix: i++ => i+=2
Workaround: run "dec" first to decimate the data

Original issue reported on code.google.com by yob...@gmail.com on 9 Apr 2009 at 8:43