[class-parse] Support class-parse --dump on java.lang.Object

[jonpryor]

Running class-parse --dump on java.lang.Object would fail:

# on macOS, JDK 1.8 installed
$ unzip /Library/Java/JavaVirtualMachines/jdk1.8.0_92.jdk/Contents/Home/jre/lib/rt.jar java/lang/Object.class
$ mono class-parse.exe --dump java/lang/Object.class
...
class-parse: Unable to read file 'java/lang/Object.class': Object reference not set to an instance of an object

Enabling verbose output (class-parse -v) didn't help:

$ mono class-parse.exe -v --dump java/lang/Object.class
Unhandled Exception:
System.IndexOutOfRangeException: Index was outside the bounds of the array.
  at Mono.Options.Option.Parse[T] (System.String value, Mono.Options.OptionContext c) [0x0005e] in <4d78dd3d6bb745d7a994cb7587b83fb2>:0
  ...

Doh!

The problem with the IndexOutOfRangeException is a bug in
Mono.Options-PCL.cs: it should be using GenericTypeArguments[0],
not GenericTypeParameters[0]. Fix that.

Once that is fixed, we see that the NullReferenceException is coming
from accessing ClassFile.SuperClass.Name, because java.lang.Object
has no superclass, and thus ClassFile.SuperClass returns null.
Properly check for that.

With those changes in place, class-parse --dump java.lang.Object
works as intended:

$ mono class-parse.exe --dump java/lang/Object.class
.class version: 52.0
...
Methods Count: 12
...
 	11: finalize ()V Protected
 		Code(10, Unknown[LineNumberTable](6))
 		Exceptions(java/lang/Throwable)