more care around generated names, fixes #60 #82 and #97

test/codegen/expect/try_catch.js

 var try_catch;
 (function(exports) {
   'use strict';
-  // Function main: () → dynamic
-  function main() {
+  // Function foo: () → dynamic
+  function foo() {
     try {
       throw "hi there";
-    } catch ($e) {
-      if (dart.is($e, core.String)) {
-        let e = $e;
+    } catch (e$) {
+      if (dart.is(e$, core.String)) {
+        let e = e$;
         let t = dart.stackTrace(e);
+      } else {
+        let e = e$;
+        let t = dart.stackTrace(e);
+        throw e;
       }
-      let e = $e;
-      let t = dart.stackTrace(e);
-      throw e;
     }
 
   }
+  // Function bar: () → dynamic
+  function bar() {
+    try {
+      throw "hi there";
+    } catch (e$) {
+      let e = e$;
+      let t = dart.stackTrace(e);
+    }
+
+  }
+  // Function main: () → dynamic
+  function main() {
+    foo();
+    bar();
+  }
   // Exports:
+  exports.foo = foo;
+  exports.bar = bar;
   exports.main = main;
 })(try_catch || (try_catch = {}));