Created attachment 288286 [details] [review]
Proposed fix

The code for vertical/horizontal movement incorrectly only sets one X/Y component of the last reference point used for smooth bezier arcs.
This implies an incorrect rendering of cases where the path contains a h/v command followed by s or t. The problem can be seen with

<?xml version="1.0" encoding="UTF-8" standalone="no"?>
<svg id="svg2" xmlns="http://www.w3.org/2000/svg" viewBox="0 0 800 300" version="1.1">
  <path fill="#AAA" stroke="#F00" d="m100,50c100,0,100,100,0,150s-100,50,0,50z"/>
  <path fill="#AAA" stroke="#F00" d="m300,50c100,0,100,100,0,150h0s-100,50,0,50z"/>
  <path fill="#AAA" stroke="#F00" d="m500,50c100,0,100,100,0,150v0s-100,50,0,50z"/>
  <path fill="#AAA" stroke="#F00" d="m700,50c100,0,100,100,0,150l0,0s-100,50,0,50z"/>
</svg>

where the 2nd 3rd and 4th paths should be rendered identical and different from the first one (they contain "v0", "h0" and "l0,0") but only the last one is correct because h/v code only resets one component of last reference point.