add tests for eval() (#3769)

closes #3768

test/compress/issue-3768.js

@@ -0,0 +1,68 @@
+mangle: {
+    mangle = {
+        toplevel: true,
+    }
+    input: {
+        var e = eval, x = 42;
+        (function() {
+            console.log(e("typeof x"));
+        })();
+    }
+    expect: {
+        var o = eval, e = 42;
+        (function() {
+            console.log(o("typeof x"));
+        })();
+    }
+    expect_stdout: "undefined"
+}
+
+compress: {
+    options = {
+        collapse_vars: true,
+        inline: true,
+        unused: true,
+    }
+    input: {
+        console.log(function() {
+            var a = 42;
+            return eval("typeof a");
+        }(), function(e) {
+            var a = null;
+            return e("typeof a");
+        }(eval), function(eval) {
+            var a = false;
+            return eval("typeof a");
+        }(eval), function(f) {
+            var a = "STRING";
+            var eval = f;
+            return eval("typeof a");
+        }(eval), function(g) {
+            var a = eval;
+            function eval() {
+                return g;
+            }
+            return eval()("typeof a");
+        }(eval));
+    }
+    expect: {
+        console.log(function() {
+            var a = 42;
+            return eval("typeof a");
+        }(), eval("typeof a"), function(eval) {
+            var a = false;
+            return eval("typeof a");
+        }(eval), function(f) {
+            var a = "STRING";
+            var eval = f;
+            return eval("typeof a");
+        }(eval), function(g) {
+            var a = eval;
+            function eval() {
+                return g;
+            }
+            return eval()("typeof a");
+        }(eval));
+    }
+    expect_stdout: "number undefined boolean string undefined"
+}