Fix prose about H and V path commands

[JeremiePat]

Hi SVGWG,

The current wording of the H command state that:

An H or h command is equivalent to an L or l command with 0 specified for the y coordinate.

This means that M1,1 l5,5 H10 is equivalent to M1,1 l5,5 L10,0 which is not the case.

All browsers (for the lack of other SVG rendering engines) consider that M1,1 l5,5 H10 is actually equivalent to M1,1 l5,5 L10,6 which makes more sens.

As a consequence I suggest the following change in prose to fix that spec issue:

An h command is equivalent to an l command with 0 specified for the y coordinate. An H command is equivalent to an L command with the y coordinate being equal to the absolute y coordinate of the current point.

Because V is worded the same way (but for the x coordinate instead of the y coordinate), I'm also suggesting an equivalent change for the V command.