Request: remove vertical edge decoration on highlights.

[Laureano]

One thing that the current way of highlighting through frames allows you to do in qpdfview is that you can highlight columns. That is unique of qpdfview and not many other readers have that capability.

But, as the highlight draws a curve, a roundness on left and right edges, that advantage is canceled or diminished because if you select a long column the highlight gets too fat and looses accuracy.

I think nothing would be lost if we get rid of that roundness.

Greetings.

qpdfview 0.4.17.99
mx linux 18.3