Fail if DynamicChannelBuffer attempts to exceed the max capacity (#258)

- Contributed by @normanmaurer

buffer/src/main/java/io/netty/buffer/DynamicChannelBuffer.java

@@ -73,6 +73,13 @@ public class DynamicChannelBuffer extends AbstractChannelBuffer {
         int minNewCapacity = writerIndex() + minWritableBytes;
         while (newCapacity < minNewCapacity) {
             newCapacity <<= 1;
+            // Check if we exceeded the maximum size of 2gb if this is the case then
+            // newCapacity == 0
+            //
+            // https://github.com/netty/netty/issues/258
+            if (newCapacity == 0) {
+                throw new IllegalStateException("buffer capacity over 2GiB");
+            }
         }
 
         ChannelBuffer newBuffer = factory().getBuffer(order(), newCapacity);