Remove panic (fixes #395) (#541)

I don't even understand why that should panic, what's wrong with values
greater than 0x0fff_ffff? If we truly wish to avoid very large dynamic
tables, we should do so when we get the large SETTINGS_HEADER_TABLE_SIZE
value, not when encoding it.

src/hpack/encoder.rs

@@ -384,10 +384,6 @@ fn encode_int<B: BufMut>(
 
     value -= low;
 
-    if value > 0x0fff_ffff {
-        panic!("value out of range");
-    }
-
     dst.put_u8(first_byte | low as u8);
     rem -= 1;
 
@@ -851,6 +847,20 @@ mod test {
         assert_eq!("sup", huff_decode(&dst[9..]));
     }
 
+    #[test]
+    fn test_large_size_update() {
+        let mut encoder = Encoder::default();
+
+        encoder.update_max_size(1912930560);
+        assert_eq!(Some(SizeUpdate::One(1912930560)), encoder.size_update);
+
+        let mut dst = BytesMut::with_capacity(6);
+        encoder
+            .encode_size_updates(&mut (&mut dst).limit(6))
+            .unwrap();
+        assert_eq!([63, 225, 129, 148, 144, 7], &dst[..]);
+    }
+
     #[test]
     #[ignore]
     fn test_evicted_overflow() {