bpo-39590: make deque.__contains__ and deque.count hold strong references (GH-18421) (GH-18423)

(cherry picked from commit c6dedde160a9fce5d049e860f586ad8f93aec822)

Co-authored-by: sweeneyde <36520290+sweeneyde@users.noreply.github.com>

Co-authored-by: sweeneyde <36520290+sweeneyde@users.noreply.github.com>
diff --git a/Modules/_collectionsmodule.c b/Modules/_collectionsmodule.c
index 45169ec..cc2b90e 100644
--- a/Modules/_collectionsmodule.c
+++ b/Modules/_collectionsmodule.c
@@ -966,7 +966,9 @@
     while (--n >= 0) {
         CHECK_NOT_END(b);
         item = b->data[index];
+        Py_INCREF(item);
         cmp = PyObject_RichCompareBool(item, v, Py_EQ);
+        Py_DECREF(item);
         if (cmp < 0)
             return NULL;
         count += cmp;
@@ -1003,7 +1005,9 @@
     while (--n >= 0) {
         CHECK_NOT_END(b);
         item = b->data[index];
+        Py_INCREF(item);
         cmp = PyObject_RichCompareBool(item, v, Py_EQ);
+        Py_DECREF(item);
         if (cmp) {
             return cmp;
         }