osutil: fix excessive decref on tuple creation failure in listdir()
The stat object would be freed on error for the same reason as the previous
patch. makestat() can be inlined, but this patch doesn't change it.
https://github.com/python/cpython/blob/2.7/Python/modsupport.c#L292
The __APPLE__ code is untested.
#if no-windows no-osx
$ mkdir -p xdgconf/hg
$ echo '[ui]' > xdgconf/hg/hgrc
$ echo 'username = foobar' >> xdgconf/hg/hgrc
$ XDG_CONFIG_HOME="`pwd`/xdgconf" ; export XDG_CONFIG_HOME
$ unset HGRCPATH
$ hg config ui.username 2>/dev/null
foobar
#endif