pthread: add dummy implementation of pthread_setcancelstate

Used by new versions of newlib in stdio functions.

components/newlib/pthread.c

@@ -8,3 +8,8 @@ int pthread_condattr_setclock(pthread_condattr_t *attr, clockid_t clock_id)
     ESP_LOGW(TAG, "%s: not yet supported!", __FUNCTION__);   
     return 0;
 }
+
+int pthread_setcancelstate(int state, int *oldstate)
+{
+    return 0;
+}