Add a dummy common.h header with a deprecation warning
diff --git a/setup.py b/setup.py
index e24f34b..b761205 100644
--- a/setup.py
+++ b/setup.py
@@ -23,6 +23,7 @@
         'include/pybind11/buffer_info.h',
         'include/pybind11/cast.h',
         'include/pybind11/chrono.h',
+        'include/pybind11/common.h',
         'include/pybind11/complex.h',
         'include/pybind11/eigen.h',
         'include/pybind11/embed.h',