To facilitate JVM experiments, implement a javac flag to opt in to alternate compilation behavior. When the flag is set:

1) Any field with an inline type is "erased" to the ref type—'Point p' becomes 'p:LPoint$ref;'. This does *not* imply any change in the language model—it's just about class file encodings.

2) The field gets a new 'RestrictedField' attribute, with format:

RestrictedField_attribute {
  u2 name_index;
  u4 length;
  u2 restricted_type;
}

'restricted_type' points to a Utf8 constant whose value is the inline type descriptor—'QPoint;'

3) Field reads and writes must use the 'LPoint$ref;' descriptor. Read results will necessarily have type 'LPoint$ref;', and may be down-cast as needed.

4) The javac class file reader recognizes these fields and infers the correct inline type for language-level interactions.

These changes should take place in a new 'type-restrictions' branch.