Add intercept-url@request-matcher-ref

[rwinch]

It would be beneficial to allow intercept-url to be configured using a reference to a RequestMatcher. For example:

<http>
    <http-basic/>
    <intercept-url request-matcher-ref="matcherRef" access="denyAll"/>
</http>

<user-service>
    <user name="user" password="password" authorities="ROLE_USER"/>
</user-service>

<b:bean id="matcherRef" class="org.springframework.security.web.util.matcher.AntPathRequestMatcher"
    c:pattern="/foo"
    c:httpMethod="GET"
    c:caseSensitive="false"/>