Fix some warnings produced by different compilers. (GH-5593) (GH-5600)

(cherry picked from commit bfe4fd5f2e96e72eecb5b8a0c7df0ac1689f3b7e)

Co-authored-by: Serhiy Storchaka <storchaka@gmail.com>
diff --git a/Python/pyhash.c b/Python/pyhash.c
index a0850d0..9e6e594 100644
--- a/Python/pyhash.c
+++ b/Python/pyhash.c
@@ -17,7 +17,7 @@
 extern "C" {
 #endif
 
-_Py_HashSecret_t _Py_HashSecret = {0};
+_Py_HashSecret_t _Py_HashSecret = {{0}};
 
 #if Py_HASH_ALGORITHM == Py_HASH_EXTERNAL
 extern PyHash_FuncDef PyHash_Func;