Add support for placeholders in @RequestMapping

@RequestMapping annotations now support ${...} placeholders.

Issue: SPR-9935

spring-web/src/main/java/org/springframework/web/bind/annotation/RequestMapping.java

@@ -266,6 +266,7 @@ public @interface RequestMapping {
 	 * Ant-style path patterns are also supported (e.g. "/myPath/*.do").
 	 * At the method level, relative paths (e.g. "edit.do") are supported
 	 * within the primary mapping expressed at the type level.
+	 * Path mapping URIs may contain placeholders (e.g. "/${connect}")
 	 * <p>In a Portlet environment: the mapped portlet modes
 	 * (i.e. "EDIT", "VIEW", "HELP" or any custom modes).
 	 * <p><b>Supported at the type level as well as at the method level!</b>