Don’t leak when partly iterated glob op is freed

Don’t leak when partly iterated glob op is freed

File::Glob keeps its own hash of arrays of file names.  Each array corresponds to one call site.  When iteration finishes, it deletes
the array.  But if iteration never finishes, and the op at the call
site is freed, the array remains.  So eval "scalar<*>" will cause a
memory leak.

We already have a mechanism for hooking the freeing of ops.  So
File::Glob can use that.