Upgrade to Netty 4.1.49.Final

[rborer]

Changelogs from 4.1.36:

• https://netty.io/news/2019/06/28/4-1-37-Final.html
• https://netty.io/news/2019/07/24/4-1-38-Final.html
• https://netty.io/news/2019/08/13/4-1-39-Final.html
• https://netty.io/news/2019/09/12/4-1-41-Final.html
• https://netty.io/news/2019/09/25/4-1-42-Final.html
• https://netty.io/news/2019/10/24/4-1-43-Final.html
• https://netty.io/news/2019/12/18/4-1-44-Final.html
• https://netty.io/news/2020/01/13/4-1-45-Final.html
• https://netty.io/news/2020/02/28/4-1-46-Final.html
• https://netty.io/news/2020/03/09/4-1-47-Final.html
• https://netty.io/news/2020/03/17/4-1-48-Final.html
• https://netty.io/news/2020/04/22/4-1-49-Final.html

[rborer]

Obsolete by commit 01fe8695ab78892266cb3aebcb4645a7b2c360f8, closing.