Add optional docstrings to getset descriptors.  Fortunately, there's
no backwards compatibility to worry about, so I just pushed the
'closure' struct member to the back -- it's never used in the current
code base (I may eliminate it, but that's more work because the getter
and setter signatures would have to change.)

As examples, I added actual docstrings to the getset attributes of a
few types: file.closed, xxsubtype.spamdict.state.
diff --git a/Objects/frameobject.c b/Objects/frameobject.c
index cb7e80a..e092ce6 100644
--- a/Objects/frameobject.c
+++ b/Objects/frameobject.c
@@ -33,7 +33,7 @@
 	return f->f_locals;
 }
 
-static struct getsetlist frame_getsetlist[] = {
+static PyGetSetDef frame_getsetlist[] = {
 	{"f_locals",	(getter)frame_getlocals, NULL, NULL},
 	{0}
 };