emit JVM InnerClasses attribute for bean info classes

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Discussion (mostly about how to unearth a stack trace) at
https://groups.google.com/d/topic/scala-internals/XTVeVEsQcGc/discussion

Initial pull request at scala/scala#768

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Imported From: https://issues.scala-lang.org/browse/SI-5983?orig=1
Reporter: @magarciaEPFL
Assignee: @magarciaEPFL
See #5985

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@magarciaEPFL said:
Fixed for GenASM in 3bd646bb2fd8512dcfa14fd7941dafe955fda5ee .

Leaving open till corresponding fix lands in GenJVM, or GenJVM is deprecated, whatever happens first.

Example comparing with and without fix:

class Outer {

  class IA

  class IB

  @scala.beans.BeanInfo
  case class B(a: IA, b: IB)

}

javap for GenASM output (-target:jvm-1.6) (similar results with -target:jvm-1.5-asm)

// Including_InnerClasses_Attribute.javap
public class Outer$BBeanInfo extends scala.beans.ScalaBeanInfo
  SourceFile: "bt4.scala"
  InnerClass: 
   public #64= #9 of #63; //B=class Outer$B of class Outer
  minor version: 0
  major version: 50
  Constant pool:
. . . 

javap for GenJVM output (-target:jvm-1.5)

// Missing_InnerClasses_Attribute.javap
public class Outer$BBeanInfo extends scala.beans.ScalaBeanInfo
  SourceFile: "bt4.scala"
  minor version: 0
  major version: 49
  Constant pool:
. . . 

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@magarciaEPFL said:
Once #5985 allows partest to check javap or ASM Textifier output, a test can be provided for this bug.