--HG--
extra : transplant_source : 8%3D%9FB%EA%E9%08%0A%7B%CB%92%ED%89%ADzL%9Du6%E9

partial application of some PyPy related changes as far as they are uncontroversial and helpful for further utility code refactorings

--HG--
extra : transplant_source : %F8%87%C7%8B%90w%7E%8EG%04C%A9%89%9B%3E%FB%8CCp%F9

--HG--
extra : transplant_source : %9F%0B%FF%0F%16%0C%25%B9%FA7%D8%25%9EDpJSE%5E%BB

--HG--
extra : transplant_source : m%879%8BW%7D%87%87%F5oYoA%ABl%88I%EF%92%FA

--HG--
extra : transplant_source : n%98%20%EE%A3N%1D%20%3F%88%2A%8B%FE%A0%01%97%9F%04%ED%23

--HG--
extra : transplant_source : fE%C2RT%7EHt%958%F4%257o%00%CB%3B%C3%B7%BA

fixed unused function warning about __pyx_clear_code_object_cache() when cleanup code is not being generated

libcpp.string supports s[0]= and s.at(0)=