Add classes that were introduced to java.lang in Java 7/8 into DEFAULT_IMPORTS

Now that Clojure 1.10 alpha-6 dropped support for Java <=7, it seems reasonable to add the classes that were newly introduced to the java.lang package in Java <=8, into Clojure's DEFAULT_IMPORTS.

Here is the list of those classes I'm aware of:

Introduced in Java 7:

• AutoCloseable
• ClassValue
• ReflectiveOperationException
• BootstrapMethodError
• SafeVarargs

Introduced in Java 8:

• FunctionalInterface

Prescreened by: Alex Miller