handle variable declaration within catch blocks (#1546)

accounts for IE8- scoping

test/compress/reduce_vars.js

@@ -605,6 +605,29 @@ inner_var_for_in_2: {
     }
 }
 
+inner_var_catch: {
+    options = {
+        evaluate: true,
+        reduce_vars: true,
+    }
+    input: {
+        try {
+            a();
+        } catch (e) {
+            var b = 1;
+        }
+        console.log(b);
+    }
+    expect: {
+        try {
+            a();
+        } catch (e) {
+            var b = 1;
+        }
+        console.log(b);
+    }
+}
+
 issue_1533_1: {
     options = {
         collapse_vars: true,

test/compress/screw-ie8.js

@@ -148,3 +148,37 @@ dont_screw_try_catch_undefined: {
         }
     }
 }
+
+reduce_vars: {
+    options = {
+        evaluate: true,
+        reduce_vars: true,
+        screw_ie8: false,
+        unused: true,
+    }
+    mangle = {
+        screw_ie8: false,
+    }
+    input: {
+        function f() {
+            var a;
+            try {
+                x();
+            } catch (a) {
+                y();
+            }
+            alert(a);
+        }
+    }
+    expect: {
+        function f() {
+            var t;
+            try {
+                x();
+            } catch (t) {
+                y();
+            }
+            alert(t);
+        }
+    }
+}