Update to 3.5.4
    
    See https://docs.python.org/3.5/whatsnew/changelog.html#python-3-5-4
    
    Remove patch 259 - workaround for magic number bump (upstream commit 93602e3).
    Remove patch 267 - pip option --system-site-packages (upstream commit db6322c).
    Remove patch 269 - multiple compilation issue with PGO (upstream commit 8489409).
    Rebase patch 55 - systemtap (for upstream commit a5c62a8e).