Pulse Width Measurement of single pulse

[blutack]

Hi, I ported the pulse measurement filter to the scalar approach as I needed it. I ending up gutting out all the amplitude measurement stuff so it's probably not suitable to incorporate as is but I can share if it's useful.

While doing this, I noticed that the filter does not work for a single pulse. The code that iterates over edges looks like this:

size_t elen = edges.size();

for(size_t i=0; i < (elen - 2); i+= 2)
{

So in the case of a single pulse with 2 edges, i < (2 - 2) on the first iteration and the loop never runs at all.

Changing the case to:

size_t elen = edges.size();

for(size_t i=0; i < (elen - 1); i+= 2)
{

it now correctly handles the single pulse case.

Thanks for this excellent project!