Initialize variables to fix compiler warnings

Warnings seen on the "AMD64 Debian PGO 3.x" buildbot. Warnings are false
positive, but variable initialization should not harm performances.

Modules/_cursesmodule.c

@@ -594,7 +594,7 @@ curses_window_addch_impl(PyCursesWindowObject *self, int group_left_1, int y,
     int attr_group = group_right_1;
     int rtn;
     int type;
-    chtype cch;
+    chtype cch = 0;
 #ifdef HAVE_NCURSESW
     wchar_t wstr[2];
     cchar_t wcval;

Modules/_pickle.c

@@ -4762,7 +4762,7 @@ static int
 load_long(UnpicklerObject *self)
 {
     PyObject *value;
-    char *s;
+    char *s = NULL;
     Py_ssize_t len;
 
     if ((len = _Unpickler_Readline(self, &s)) < 0)
@@ -4993,7 +4993,7 @@ load_unicode(UnpicklerObject *self)
 {
     PyObject *str;
     Py_ssize_t len;
-    char *s;
+    char *s = NULL;
 
     if ((len = _Unpickler_Readline(self, &s)) < 0)
         return -1;
@@ -5732,7 +5732,7 @@ load_put(UnpicklerObject *self)
     PyObject *key, *value;
     Py_ssize_t idx;
     Py_ssize_t len;
-    char *s;
+    char *s = NULL;
 
     if ((len = _Unpickler_Readline(self, &s)) < 0)
         return -1;