rename --prop-cache to --name-cache

... and support storing there variable names as well, to help with multiple
invocations when mangling toplevel.

lib/scope.js

@@ -67,18 +67,26 @@ SymbolDef.prototype = {
                     || this.orig[0] instanceof AST_SymbolDefun));
     },
     mangle: function(options) {
-        if (!this.mangled_name && !this.unmangleable(options)) {
+        var cache = options.cache && options.cache.props;
+        if (this.global && cache && cache.has(this.name)) {
+            this.mangled_name = cache.get(this.name);
+        }
+        else if (!this.mangled_name && !this.unmangleable(options)) {
             var s = this.scope;
             if (!options.screw_ie8 && this.orig[0] instanceof AST_SymbolLambda)
                 s = s.parent_scope;
             this.mangled_name = s.next_mangled(options, this);
+            if (this.global && cache) {
+                cache.set(this.name, this.mangled_name);
+            }
         }
     }
 };
 
 AST_Toplevel.DEFMETHOD("figure_out_scope", function(options){
     options = defaults(options, {
-        screw_ie8: false
+        screw_ie8: false,
+        cache: null
     });
 
     // pass 1: setup scope chaining and handle definitions
@@ -183,6 +191,10 @@ AST_Toplevel.DEFMETHOD("figure_out_scope", function(options){
         }
     });
     self.walk(tw);
+
+    if (options.cache) {
+        this.cname = options.cache.cname;
+    }
 });
 
 AST_Scope.DEFMETHOD("init_scope_vars", function(nesting){
@@ -344,6 +356,15 @@ AST_Toplevel.DEFMETHOD("mangle_names", function(options){
     // the AST_SymbolDeclaration that it points to).
     var lname = -1;
     var to_mangle = [];
+
+    if (options.cache) {
+        this.globals.each(function(symbol){
+            if (options.except.indexOf(symbol.name) < 0) {
+                to_mangle.push(symbol);
+            }
+        });
+    }
+
     var tw = new TreeWalker(function(node, descend){
         if (node instanceof AST_LabeledStatement) {
             // lname is incremented when we get to the AST_Label
@@ -378,6 +399,10 @@ AST_Toplevel.DEFMETHOD("mangle_names", function(options){
     });
     this.walk(tw);
     to_mangle.forEach(function(def){ def.mangle(options) });
+
+    if (options.cache) {
+        options.cache.cname = this.cname;
+    }
 });
 
 AST_Toplevel.DEFMETHOD("compute_char_frequency", function(options){