Better support try/catch comments (#607)

Uses the same technique as for if/then/else. Added a helper function to make it easier.

Fixes #601

tests/comments/try.js

@@ -0,0 +1,13 @@
+// comment 1
+try {
+  // comment 2
+}
+// comment 3
+catch(e) {
+  // comment 4
+}
+// comment 5
+finally // comment 6
+{
+  // comment 7
+}