fix(menu): incorrect text alignment in IE/Edge (#3268)

Fixes #3254.

Author: crisbeto

src/lib/core/style/_menu-common.scss

@@ -32,13 +32,17 @@ $mat-menu-side-padding: 16px !default;
 
   font-size: $mat-menu-font-size;
   font-family: $mat-font-family;
-  text-align: start;
+  text-align: left;
   text-decoration: none;   // necessary to reset anchor tags
 
   &[disabled] {
     cursor: default;
   }
 
+  [dir='rtl'] & {
+    text-align: right;
+  }
+
   .mat-icon {
     margin-right: 16px;