Initial vendor packages

Signed-off-by: Valentin Popov <valentin@popov.link>

vendor/backtrace/tests/accuracy/auxiliary.rs

@@ -0,0 +1,15 @@
+#[inline(never)]
+pub fn callback<F>(f: F)
+where
+    F: FnOnce((&'static str, u32)),
+{
+    f((file!(), line!()))
+}
+
+#[inline(always)]
+pub fn callback_inlined<F>(f: F)
+where
+    F: FnOnce((&'static str, u32)),
+{
+    f((file!(), line!()))
+}