rust-cpython: move $leaked struct out of macro
It wasn't easy to hack the $leaked struct since errors in macro would
generate lots of compile errors. Let's make it a plain struct so we can
easily extend it.
PyLeakedRef keeps a more generic PyObject instead of the $name struct
since it no longer has to call any specific methods implemented by
the $name class. $leaked parameter in py_shared_iterator!() is kept
for future change.
$ rm -rf a
$ hg init a
$ cd a
$ echo a > a
$ hg ci -Am0
adding a
$ hg tag t1 # 1
$ hg tag --remove t1 # 2
$ hg co 1
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
$ hg tag -f -r0 t1
$ hg tags
tip 3:a49829c4fc11
t1 0:f7b1eb17ad24
$ cd ..