Bump AspectJ libraries in 'lib' subfolders to 1.9.21.1

This reproduces regression bug #285 when running
org.aspectj.systemtest.ajc171.NewFeatures::testSharedCache.

Signed-off-by: Alexander Kriegisch <Alexander@Kriegisch.name>

lib/aspectj/lib/readme.txt

@@ -0,0 +1,6 @@
+AspectJ_JDK_Update
+
+Always add latest AspectJ core libraries (aspectjrt.jar, aspectjweaver.jar, aspectjtools.jar) here to ensure that
+relevant integration tests run with the latest versions. Having missed the update in the past has led to regression bugs
+to occur, e.g. https://github.com/eclipse-aspectj/aspectj/issues/285, which was introduced during the fix for
+https://github.com/eclipse-aspectj/aspectj/issues/277.

lib/test/readme.txt

@@ -0,0 +1,3 @@
+AspectJ_JDK_Update
+
+Always add latest aspectjrt.jar here to ensure that relevant integration tests run with the latest versions.