Streamline log enablement (#64)

* Remove log_enabled statements around annotate calls, which are already guarded against annotations_enabled

* Use a trace_enabled!() macro that follows the same logic as trace!() to find if additional traces have been enabled or not

src/lib.rs

@@ -22,6 +22,12 @@ macro_rules! trace {
     };
 }
 
+macro_rules! trace_enabled {
+    () => {
+        cfg!(feature = "trace-log")
+    };
+}
+
 pub(crate) mod cfg;
 pub(crate) mod domtree;
 pub mod indexset;