Implemented GH#3 Abstract keyword cannot be used with private members

lib/member_builder.js

@@ -77,6 +77,15 @@ exports.buildMethod = function(
     var prev_data = scanMembers( members, name, base ),
         prev      = ( prev_data ) ? prev_data.member : null;
 
+    // do not permit private abstract methods (doesn't make sense, since
+    // they cannot be inherited/overridden)
+    if ( keywords[ 'abstract' ] && keywords[ 'private' ] )
+    {
+        throw TypeError(
+            "Method '" + name + "' cannot be both private and abstract"
+        );
+    }
+
     // search for any previous instances of this member
     if ( prev )
     {

test/test-member_builder-method.js

@@ -276,3 +276,18 @@ mb_common.assertCommon();
     );
 } )();
 
+
+/**
+ * It does not make sense to be able to declare abstract private methods, since
+ * they cannot be inherited and overridden by subtypes.
+ */
+( function testCannotDeclareAbstractPrivateMethods()
+{
+    mb_common.value = function() {};
+
+    assert.throws( function()
+    {
+        mb_common.buildMemberQuick( { 'private': true, 'abstract': true } );
+    }, TypeError, "Cannot declare private abstract method" );
+} )();
+