dtransform mute chat to use relative durations

instead of absolute timestamps

deltachat-ffi/src/tools.rs

@@ -0,0 +1,8 @@
+use std::time::SystemTime;
+
+pub(crate) fn time() -> i64 {
+    SystemTime::now()
+        .duration_since(SystemTime::UNIX_EPOCH)
+        .unwrap_or_default()
+        .as_secs() as i64
+}