Allow to customize separator for messaging destinations

In order to be able to use separators like "." (used by default
by most broker relays) instead of "/" for destination patterns
handling, the PathMatcher used in spring-messaging can now
be customized easily thanks to XML websocket namespace
or JavaConfig.

AntPathMatcher has been updated in order to use the configured path
separator instead of an hardcoded "/" for path concatenation.
Extension handling is now disabled when the "." separator is configured.

Issue: SPR-11660

spring-core/src/test/java/org/springframework/util/AntPathMatcherTests.java

@@ -606,4 +606,10 @@ public class AntPathMatcherTests {
 		assertTrue(pathMatcher.stringMatcherCache.isEmpty());
 	}
 
+	@Test
+	public void noExtensionHandlingWithDotSeparator() {
+		pathMatcher.setPathSeparator(".");
+		assertEquals("/*.html.hotel.*", pathMatcher.combine("/*.html", "hotel.*"));
+	}
+
 }