deserializeLambda should not use encoded class name

`javaBinaryName` returns the internal name of a class.
Also used in BTypesFromsymbols.classBTypeFromSymbol.

Weirdly, this was discovered due to a bizarre osgi bnd error:

```
[bnd] # addAll '/Users/luc/scala/scala/build/pack/lib/scala-library.jar' with :,
[bnd] # addAll '/Users/luc/scala/scala/build/osgi/scala-library.bnd' with ,
[bnd] 1 ERRORS
[bnd]  The default package '.' is not permitted by the Import-Package syntax.
[bnd]  This can be caused by compile errors in Eclipse because Eclipse creates
[bnd] valid class files regardless of compile errors.
[bnd] The following package(s) import from the default package [scala.collection.generic, scala.sys.process, scala.collection.parallel.mutable, scala.util, scala.collection.parallel.immutable, scala.reflect, scala.concurrent.impl, scala.util.hashing, scala.collection.parallel, scala.collection.convert, scala.io, scala, scala.collection.concurrent, scala.util.control, scala.beans, scala.concurrent.duration, scala.collection, scala.runtime, scala.math, scala.collection.mutable, scala.concurrent, scala.sys, scala.collection.immutable, scala.ref, scala.util.matching]
[bnd] /Users/luc/scala/scala/build/osgi/scala-library.bnd: bnd failed
```

Lukas diagnosed it as a problem of the generated `$deserializeLambda$` function:

One example is `scala/App$class`. Its bytecode contains this:
```
  private static synthetic $deserializeLambda$(Ljava/lang/invoke/SerializedLambda;)Ljava/lang/Object;
    GETSTATIC scala$divApp$class.$deserializeLambdaCache$ : Ljava/util/Map;
    [...]
```
so it's a static field read of a top-level class.

`$div` should obviously be `/` (which this commit rectifies)

Author: lrytz

src/compiler/scala/tools/nsc/backend/jvm/BCodeHelpers.scala

@@ -715,7 +715,8 @@ abstract class BCodeHelpers extends BCodeIdiomatic with BytecodeWriters {
       {
         val mv = cw.visitMethod(ACC_PRIVATE + ACC_STATIC + ACC_SYNTHETIC, "$deserializeLambda$", "(Ljava/lang/invoke/SerializedLambda;)Ljava/lang/Object;", null, null)
         mv.visitCode()
-        mv.visitFieldInsn(GETSTATIC, clazz.javaBinaryName.encoded, "$deserializeLambdaCache$", "Ljava/util/Map;")
+        // javaBinaryName returns the internal name of a class. Also used in BTypesFromsymbols.classBTypeFromSymbol.
+        mv.visitFieldInsn(GETSTATIC, clazz.javaBinaryName.toString, "$deserializeLambdaCache$", "Ljava/util/Map;")
         mv.visitVarInsn(ASTORE, 1)
         mv.visitVarInsn(ALOAD, 1)
         val l0 = new asm.Label()
@@ -725,7 +726,7 @@ abstract class BCodeHelpers extends BCodeIdiomatic with BytecodeWriters {
         mv.visitMethodInsn(INVOKESPECIAL, "java/util/HashMap", "<init>", "()V", false)
         mv.visitVarInsn(ASTORE, 1)
         mv.visitVarInsn(ALOAD, 1)
-        mv.visitFieldInsn(PUTSTATIC, clazz.javaBinaryName.encoded, "$deserializeLambdaCache$", "Ljava/util/Map;")
+        mv.visitFieldInsn(PUTSTATIC, clazz.javaBinaryName.toString, "$deserializeLambdaCache$", "Ljava/util/Map;")
         mv.visitLabel(l0)
         mv.visitFrame(asm.Opcodes.F_APPEND,1, Array("java/util/Map"), 0, null)
         mv.visitMethodInsn(INVOKESTATIC, "java/lang/invoke/MethodHandles", "lookup", "()Ljava/lang/invoke/MethodHandles$Lookup;", false)