repeat.t: Correct comment

When a57276195 changed the eq to is(), the comment was not updated.
The test still works.  (I tried introducing the bug it was testing
for via SP--, and it failed as expected.)
[perl #123161] Add %B::Op_private::ops_using
Have Deparse use %B::Op_private::ops_using
current_sub.t: Test sub(){__SUB__}

If the constant inlining algorithm changes, we need to make sure not
to break sub(){__SUB__} accidentally.

Sometimes __SUB__ gets optimised to a constant.  Constant inlining
searches the op tree for constants.  Currently we are saved by the
fact that the search happens before the peephole optimizer does the
conversion.