Move to stock ASM

[lrytz]

Here's what's required to move to stock ASM

Repackage

Change org.objectweb.asm to scala.tools.asm.

• Jar Jar (SO answer) - last release in 2012 though
• Proguard (SO answer), with some scripting to get all class names

Get Rid of our Patches

• Class CustomAttr.
  • Class is in the asm package to allow accessing the byte array directly.
  • Can we avoid using this class by emitting attributes differently in the backend?
• Expose maxLocals / maxStack in MethodWriter.
  • Should be fixed by implementing a visitor that computes those values, which will also be more efficient. See https://github.com/scala-opt/scala/issues/1.
• Associate LabelNodes with their Label.
  • Not sure why we need this patch, need to try out what breaks if we revert it.
  • The patch seems to be not recommended, see this thread.
• Allow setting stack values in analysis frames
  • This might go upstream.
• Multiple methods for initializing analysis values
  • This might go upstream.

The more cosmetic changes can be handed upstream or dropped.