Fix --mangle-props and --mangle-props=unquoted

Fixes: #1247

Fix --mangle-props and --name-cache inconsistency.
AST_Dot and AST_Sub properties are now mangled by --mangle-props
without regard to being used in an assignment statement.

Note: if --mangle-props is used then *all* javascript files used must
be uglified with the same mangle options.

Fix the ignore_quoted=true mangle option, also known as
`--mangle-props=unquoted`.  If a given property is quoted anywhere
it will not be mangled in any quoted or non-quoted context.

lib/propmangle.js

@@ -86,27 +86,22 @@ function mangle_properties(ast, options) {
 
     var names_to_mangle = [];
     var unmangleable = [];
+    var ignored = {};
 
     // step 1: find candidates to mangle
     ast.walk(new TreeWalker(function(node){
         if (node instanceof AST_ObjectKeyVal) {
-            if (!(ignore_quoted && node.quote))
-                add(node.key);
+            add(node.key, ignore_quoted && node.quote);
         }
         else if (node instanceof AST_ObjectProperty) {
             // setter or getter, since KeyVal is handled above
             add(node.key.name);
         }
         else if (node instanceof AST_Dot) {
-            if (this.parent() instanceof AST_Assign) {
-                add(node.property);
-            }
+            add(node.property);
         }
         else if (node instanceof AST_Sub) {
-            if (this.parent() instanceof AST_Assign) {
-                if (!ignore_quoted)
-                    addStrings(node.property);
-            }
+            addStrings(node.property, ignore_quoted);
         }
     }));
 
@@ -154,13 +149,19 @@ function mangle_properties(ast, options) {
     }
 
     function should_mangle(name) {
+        if (ignore_quoted && name in ignored) return false;
         if (regex && !regex.test(name)) return false;
         if (reserved.indexOf(name) >= 0) return false;
         return cache.props.has(name)
             || names_to_mangle.indexOf(name) >= 0;
     }
 
-    function add(name) {
+    function add(name, ignore) {
+        if (ignore) {
+            ignored[name] = true;
+            return;
+        }
+
         if (can_mangle(name))
             push_uniq(names_to_mangle, name);
 
@@ -184,7 +185,7 @@ function mangle_properties(ast, options) {
         return mangled;
     }
 
-    function addStrings(node) {
+    function addStrings(node, ignore) {
         var out = {};
         try {
             (function walk(node){
@@ -194,7 +195,7 @@ function mangle_properties(ast, options) {
                         return true;
                     }
                     if (node instanceof AST_String) {
-                        add(node.value);
+                        add(node.value, ignore);
                         return true;
                     }
                     if (node instanceof AST_Conditional) {