check and restrict size hint values

Could not reproduce a crash, but may mess up window geometry, etc.

Test program below to give an idea:

cc repro.c -o repro -lX11; ./repro

int
main(void)
{
	Display *d;
	int screen;
	Window root;
	Window win;

	d = XOpenDisplay(NULL);
	if (!d) {
		fprintf(stderr, "XOpenDisplay failed\n");
		return 1;
	}
	screen = DefaultScreen(d);
	root = RootWindow(d, screen);

	win = XCreateSimpleWindow(d, root, 0, 0, 100, 100, 0, 0, 0);
	if (!win) {
		fprintf(stderr, "XCreateSimpleWindow failed\n");
		XCloseDisplay(d);
		return 1;
	}

	//XMapWindow(d, win);
	XMapRaised(d, win);

	XSizeHints h = {0};
	h.flags = PResizeInc | PBaseSize | PMinSize;
	h.width_inc = -1;
	h.height_inc = -1;
	h.base_width = INT_MIN + 500; /* window is 500px wide */
	h.base_height = 0;

	h.min_width = ~0L;
	h.min_height = ~0L;

	XSetWMNormalHints(d, win, &h);

	sleep(3);

	//XDestroyWindow(d, win);

	XCloseDisplay(d);

	return 0;
}

dwm.c

@@ -1968,32 +1968,32 @@ updatesizehints(Client *c)
 		/* size is uninitialized, ensure that size.flags aren't used */
 		size.flags = PSize;
 	if (size.flags & PBaseSize) {
-		c->basew = size.base_width;
+		c->basew = MAX(0, size.base_width);
-		c->baseh = size.base_height;
+		c->baseh = MAX(0, size.base_height);
 	} else if (size.flags & PMinSize) {
-		c->basew = size.min_width;
+		c->basew = MAX(0, size.min_width);
-		c->baseh = size.min_height;
+		c->baseh = MAX(0, size.min_height);
 	} else
 		c->basew = c->baseh = 0;
 	if (size.flags & PResizeInc) {
-		c->incw = size.width_inc;
+		c->incw = MAX(0, size.width_inc);
-		c->inch = size.height_inc;
+		c->inch = MAX(0, size.height_inc);
 	} else
 		c->incw = c->inch = 0;
 	if (size.flags & PMaxSize) {
-		c->maxw = size.max_width;
+		c->maxw = MAX(0, size.max_width);
-		c->maxh = size.max_height;
+		c->maxh = MAX(0, size.max_height);
 	} else
 		c->maxw = c->maxh = 0;
 	if (size.flags & PMinSize) {
-		c->minw = size.min_width;
+		c->minw = MAX(0, size.min_width);
-		c->minh = size.min_height;
+		c->minh = MAX(0, size.min_height);
 	} else if (size.flags & PBaseSize) {
-		c->minw = size.base_width;
+		c->minw = MAX(0, size.base_width);
-		c->minh = size.base_height;
+		c->minh = MAX(0, size.base_height);
 	} else
 		c->minw = c->minh = 0;
-	if (size.flags & PAspect) {
+	if ((size.flags & PAspect) && size.min_aspect.x > 0 && size.max_aspect.y > 0) {
 		c->mina = (float)size.min_aspect.y / size.min_aspect.x;
 		c->maxa = (float)size.max_aspect.x / size.max_aspect.y;
 	} else