PR libstdc++/80229 restore support for shared_ptr<function type>
PR libstdc++/80229
* include/bits/shared_ptr_base.h
(__shared_ptr::_M_enable_shared_from_this_with): Change parameters to
non-const and then use remove_cv to get unqualified type.
* testsuite/20_util/enable_shared_from_this/members/const.cc: Don't
cast away constness on object created const.
* testsuite/20_util/shared_ptr/cons/80229.cc: New test.
git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@246520 138bc75d-0d04-0410-961f-82ee72b054a4