include *.hpp test files in sdist

MANIFEST.in

@@ -21,7 +21,7 @@ include Demos/Makefile*
 recursive-include Cython/Debugger/Tests *.pyx *.pxd *.c *.h
 recursive-include Cython/Utility *.pyx *.pxd *.c *.h *.cpp
 recursive-include Tools *
-recursive-include tests *.pyx *.pxd *.pxi *.py *.h *.BROKEN bugs.txt
+recursive-include tests *.pyx *.pxd *.pxi *.py *.h *.hpp *.BROKEN bugs.txt
 recursive-include tests *_lib.cpp *.srctree
 recursive-include docs *
 include runtests.py