TODO for java.lang.reflect Native side:

- Field.c: if wrapper classes are wrong in setNative(), it
  will set the field to null before throwing an exception,
  or possibly observe undefined behavior.  Put error
  checking in there.

- Member classes: cache some native info regarding the type
  of the return value / field value, and maybe the argument
  types as well, so that IsAssignableFrom needs to be
  called less.

- Overhaul checkMemberAccess to call
  SecurityManager.checkMember(...).  At least I think this
  needs to be done.  Though the spec wants even more specific
  tests, so perhaps not.

- test Method,Field,Constructor.
