Add option to use javap instead of asm

[lrytz]

ASM desugars certain details when disassembling classfiles, for example it eliminates redundant line numbers:

$ javap -v -cp a C
...
  public void t();
...
      LineNumberTable:
        line 2: 0
        line 3: 0
        line 4: 3

whereas

$ asm a/C.class
$ cat a/C.asm
...
  public t()V
   L0
    LINENUMBER 3 L0
    LDC ""
   L1
    ASTORE 1
   L2
    LINENUMBER 4 L2

[retronym]

I haven't implemented this yet, but I have add -r ("raw") mode to show more details with ASM. It disables sorting of members, shows the Scala sig annotation and all attributes, and includes local variable names and stack map entries.

[retronym]

The difficulty here is finding a way to call javap without forking (which is expensive for lots of files), that will also work across a range of JDK versions. The REPL has some code do to this but it has been somewhat fragile.