Clean up, unify and accurately calculate edge distance with client move/resize

actions, so as to not lose windows off the edge.

inspired by diffs (and feedback) from Vadim Vygonets.

client.c

@@ -470,6 +470,24 @@ client_config(struct client_ctx *cc)
 	XSendEvent(X_Dpy, cc->win, False, StructureNotifyMask, (XEvent *)&cn);
 }
 
+void
+client_ptr_inbound(struct client_ctx *cc, int getpos)
+{
+	if (getpos)
+		xu_ptr_getpos(cc->win, &cc->ptr.x, &cc->ptr.y);
+
+	if (cc->ptr.x < 0)
+		cc->ptr.x = 0;
+	else if (cc->ptr.x > cc->geom.w - 1)
+		cc->ptr.x = cc->geom.w - 1;
+	if (cc->ptr.y < 0)
+		cc->ptr.y = 0;
+	else if (cc->ptr.y > cc->geom.h - 1)
+		cc->ptr.y = cc->geom.h - 1;
+
+	client_ptrwarp(cc);
+}
+
 void
 client_ptrwarp(struct client_ctx *cc)
 {