Fix bump llhttp to v8.1.1

.gitmodules

@@ -1,4 +1,4 @@
 [submodule "vendor/llhttp"]
     path = vendor/llhttp
     url = https://github.com/nodejs/llhttp.git
-    branch = v8.1.1
+    branch = v8.x

tests/test_http_parser.py

@@ -694,6 +694,7 @@ def test_http_response_parser_bad(response: Any) -> None:
         response.feed_data(b"HTT/1\r\n\r\n")
 
 
+@pytest.mark.skipif(not NO_EXTENSIONS, reason="Behaviour has changed in C parser")
 def test_http_response_parser_code_under_100(response: Any) -> None:
     msg = response.feed_data(b"HTTP/1.1 99 test\r\n\r\n")[0][0][0]
     assert msg.code == 99

vendor/README.rst

@@ -0,0 +1,20 @@
+LLHTTP
+======
+
+To build the llhttp parser, first get/update the submodule (to update to a
+newer release, add ``--remote`` and check the branch in .gitmodules)::
+
+    git submodule update --init --recursive
+
+Then build llhttp::
+
+    cd vendor/llhttp/
+    npm install
+    make
+
+Then build our parser::
+
+    cd -
+    make cythonize
+
+Then you can build or install it with ``python -m build`` or ``pip install .``