CGLIB 3 has been released in order to depend on ASM 4, which Spring now
depends on internally (see previous commit).

This commit eliminates spring-beans' optional dependency on cglib-nodep
v2.2 and instead repackages net.sf.cglib => org.springframework.cglib
much in the same way we have historically done with ASM.

This change is beneficial to users in several ways:

 - Eliminates the need to manually add CGLIB to the application
   classpath; especially important for the growing number of
   @Configuration class users. Java-based configuration functionality,
   along with proxy-target-class and method injection features now
   work 'out of the box' in Spring 3.2.

 - Eliminates the possibility of conflicts with other libraries that
   may dependend on differing versions of CGLIB, e.g. Hibernate
   3.3.1.ga and its dependency on CGLIB 2.1.3 would easily cause a
   conflict if the application were depending on CGLIB 3 for
   Spring-related purposes.

 - Picks up CGLIB 3's changes to support ASM 4, meaning that CGLIB is
   that much less likely to work well in a Java 7 environment due to
   ASM 4's support for transforming classes with invokedynamic
   bytecode instructions.

On CGLIB and ASM:

  CGLIB's own dependency on ASM is also transformed along the way to
  depend on Spring's repackaged org.springframework.asm, primarily to
  eliminate unnecessary duplication of ASM classfiles in spring-core and
  in the process save around 100K in the final spring-core JAR file size.

  It is coincidental that spring-core and CGLIB currently depend on the
  exact same version of ASM (4.0), but it is also unlikely to change any
  time soon. If this change does occur and versions of ASM drift, then
  the size optimization mentioned above will have to be abandoned. This
  would have no compatibility impact, however, so this is a reasonable
  solution now and for the forseeable future.

On a mysterious NoClassDefFoundError:

  During the upgrade to CGLIB 3.0, Spring test cases began failing due to
  NoClassDefFoundErrors being thrown from CGLIB's DebuggingClassWriter
  regarding its use of asm-util's TraceClassVisitor type. previous
  versions of cglib-nodep, particularly 2.2, did not cause this behavior,
  even though cglib-nodep has never actually repackaged and bundled
  asm-util classes. The reason for these NoClassDefFoundErrors occurring
  now is still not fully understood, but appears to be due to subtle JVM
  bytecode preverification rules. The hypothesis is that due to minor
  changes in DebuggingClassWriter such as additional casts, access to
  instance variables declared in the superclass, and indeed a change in
  the superclass hierarchy, preverification may be kicking in on the
  toByteArray method body, at which point the reference to the missing
  TraceClassVisitor type is noticed and the NCDFE is thrown. For this
  reason, a dummy implementation of TraceClassVisitor has been added to
  spring-core in the org.springframework.asm.util package. This class
  simply ensures that Spring's own tests never result in the NCDFE
  described above, and more importantly that Spring's users never
  encounter the same.

Other changes include:

 - rename package-private Cglib2AopProxy => CglibAopProxy
 - eliminate all 'cglibAvailable' checks, warnings and errors
 - eliminate all 'CGLIB2' language in favor of 'CGLIB'
 - eliminate all mention in reference and java docs of needing to add
   cglib(-nodep) to one's application classpath

Issue: SPR-9669