Fixed memory leak with large objects

Deallocating closed large objects failed to decrement the connection
refcount. The fact the lobject is closed doesn't matter for refcount.
Issue detected by the always useful scripts/refcounter.py

With an extra bit of unrequested whitespace love.

NEWS

@@ -17,6 +17,7 @@ What's new in psycopg 2.5.4
   PostgreSQL but not documented.
 - Make sure the internal `_psycopg.so` module can be imported stand-alone
   (to allow modules juggling such as the one described in :ticket:`#201`).
+- Fixed memory leak with large objects (regression introduced in 2.5.3).
 
 
 What's new in psycopg 2.5.3

psycopg/lobject_type.c

@@ -52,7 +52,7 @@ psyco_lobj_close(lobjectObject *self, PyObject *args)
        opened large objects */
     if (!lobject_is_closed(self)
         && !self->conn->autocommit
-	&& self->conn->mark == self->mark)
+        && self->conn->mark == self->mark)
     {
         Dprintf("psyco_lobj_close: closing lobject at %p", self);
         if (lobject_close(self) < 0)
@@ -171,14 +171,14 @@ psyco_lobj_seek(lobjectObject *self, PyObject *args)
     int pos=0;
 
     if (!PyArg_ParseTuple(args, "i|i", &offset, &whence))
-    	return NULL;
+        return NULL;
 
     EXC_IF_LOBJ_CLOSED(self);
     EXC_IF_LOBJ_LEVEL0(self);
     EXC_IF_LOBJ_UNMARKED(self);
 
     if ((pos = lobject_seek(self, offset, whence)) < 0)
-    	return NULL;
+        return NULL;
 
     return PyInt_FromLong((long)pos);
 }
@@ -198,7 +198,7 @@ psyco_lobj_tell(lobjectObject *self, PyObject *args)
     EXC_IF_LOBJ_UNMARKED(self);
 
     if ((pos = lobject_tell(self)) < 0)
-    	return NULL;
+        return NULL;
 
     return PyInt_FromLong((long)pos);
 }
@@ -333,11 +333,10 @@ lobject_setup(lobjectObject *self, connectionObject *conn,
         return -1;
     }
 
+    Py_INCREF((PyObject*)conn);
     self->conn = conn;
     self->mark = conn->mark;
 
-    Py_INCREF((PyObject*)self->conn);
-
     self->fd = -1;
     self->oid = InvalidOid;
 
@@ -358,8 +357,8 @@ lobject_dealloc(PyObject* obj)
     if (self->conn && self->fd != -1) {
         if (lobject_close(self) < 0)
             PyErr_Print();
-        Py_XDECREF((PyObject*)self->conn);
     }
+    Py_CLEAR(self->conn);
     PyMem_Free(self->smode);
 
     Dprintf("lobject_dealloc: deleted lobject object at %p, refcnt = "