Depend on asm-debug-all even for regular compile

Otherwise:

* it is too difficult to debug,
* raw types have to be used since the "non debug" asm jars don't have generics
  information.

Only 100k more of dependencies but hey, Guava is 2 MiB and this is 2014.
InstructionGroupPreparer: simplify String md5 update method
InstructionGroupPreparer: use Guava's Preconditions
InstructionGroupPreparer: change method override

One override was deprecated.