Issue #19553: PEP 453 - "make install" and "make altinstall" now install or

upgrade pip by default, using the bundled pip provided by the new ensurepip
module.  A new configure option, --with-ensurepip[=upgrade|install|no], is
available to override the default ensurepip "--upgrade" option.  The option
can also be set with "make [alt]install ENSUREPIP=[upgrade|install\no]".