Rebase default branch (dpdk-2011-focal) (#33)

* Ensure that kMaxBurst is explicitly defined

kMaxBurst was declared and assigned a value, but not explicitly defined. This can cause issues when linking in cases where a reference
may be taken of kMaxBurst (say, passing it to std::min()) and the constant can't be fully optimized out.

This was actually fixed years ago in #522 but ended up being reverted accidentally during a refactor in #820.

With C++17 now, we don't have to put the definition in a source file, we can just add inline and that takes care of it.

README.md

@@ -21,4 +21,4 @@ To install BESS on Linux quickly, you can download the binary from [Release](htt
     make -C core/kmod # Build the kernel module (optional)
     bessctl/bessctl
 
-Documentation can be found [here](https://github.com/omec-project/bess/wiki/). Please consider [contributing](https://github.com/omec-project/bess/wiki/How-to-Contribute) to the project!!
+Documentation can be found [here](https://github.com/omec-project/bess/wiki/). Please consider [contributing](https://github.com/omec-project/bess/wiki/How-to-Contribute) to the project!