[perl #89544] Non-eval closures don’t need CvOUTSIDE

[perl #89544] Non-eval closures don’t need CvOUTSIDE

A closure doesn’t need an outside pointer at run time, unless it has a
string eval in it.  CvOUTSIDE is only used at compilation time to look
up variables by name.

Since CvOUTSIDE is reference-counted, a closure can unnecessarily hang
on to variables it is not using (see the test in the diff).  So stop
setting it when cloning a closure, unless it is needed for eval.