feat: prevent horizontal menu items wrapping

components/menu/demo/horizontal.md

@@ -37,6 +37,7 @@ class App extends React.Component {
         onClick={this.handleClick}
         selectedKeys={[this.state.current]}
         mode="horizontal"
+        triggerSubMenuAction="click"
       >
         <Menu.Item key="mail">
           <Icon type="mail" />Navigation One
@@ -44,7 +45,7 @@ class App extends React.Component {
         <Menu.Item key="app" disabled>
           <Icon type="appstore" />Navigation Two
         </Menu.Item>
-        <SubMenu title={<span><Icon type="setting" />Navigation Three - Submenu</span>}>
+        <SubMenu title={<span className="submenu-title-wrapper"><Icon type="setting" />Navigation Three - Submenu</span>}>
           <MenuItemGroup title="Item 1">
             <Menu.Item key="setting:1">Option 1</Menu.Item>
             <Menu.Item key="setting:2">Option 2</Menu.Item>

components/menu/style/index.less

@@ -179,6 +179,10 @@
       position: absolute;
       border-radius: @border-radius-base;
       z-index: @zindex-dropdown;
+
+      .submenu-title-wrapper {
+        padding-right: 20px;
+      }
     }
 
     > .@{menu-prefix-cls} {
@@ -262,12 +266,13 @@
     border-bottom: @border-width-base @border-style-base @border-color-split;
     box-shadow: none;
     line-height: 46px;
+    white-space: nowrap;
 
     > .@{menu-prefix-cls}-item,
     > .@{menu-prefix-cls}-submenu {
       position: relative;
       top: 1px;
-      float: left;
+      display: inline-block;
       border-bottom: 2px solid transparent;
 
       &:hover,