Update qslim.h

also complete the cut off sentence in the V comment

Former-commit-id: bae373e510f943a9746c6041bba28410c79df971

include/igl/qslim.h

@@ -18,7 +18,11 @@ namespace igl
   // mesh can have open boundaries but should be edge-manifold.
   //
   // Inputs:
-  //   V  #V by dim list of vertex positions. Assumes that vertices w
+  //   V  #V by dim list of vertex positions. Assumes that vertices with
+  //     infinite coordinates are "points at infinity" being used to close up
+  //     boundary edges with faces. This allows special subspace quadrice for
+  //     boundary edges: There should never be more than one "point at
+  //     infinity" in a single triangle.
   //   F  #F by 3 list of triangle indices into V
   //   max_m  desired number of output faces
   // Outputs: