v.to.points: clarify user is not able to control where points end up

[jidanni]

In man v.to.points at

"The dmax parameter is the maximum limit but not an exact distance."

then do mention

"A complicated internal algorithm is used to place points at certain points best representing the line."

before saying

"To place points with exact distance from the beginning of the vector line the user should use v.segment."

That way the user would finally understand that he is not able to control the exact distances where points end up, and stop trying. In fact it would be good to say that to!