Determine whether or not the given class is an aspect, as reported
by AspectJ's AjTypeSystem.
Will simply return false if the supposed aspect is
invalid (such as an extension of a concrete aspect class).
Will return true for some aspects that Spring AOP cannot process,
such as those with unsupported instantiation models.
Use the validate(java.lang.Class<?>) method to handle these cases if necessary.
clazz - the supposed annotation-style AspectJ class
whether or not this class is recognized by AspectJ as an aspect class