As reported in bug #46207, change 30633 to PerlIO_exportFILE() and

As reported in bug #46207, change 30633 to PerlIO_exportFILE() and
PerlIO_releaseFILE() to manage the reference counts of fds correctly
has the side effect of making some XS modules "leak" descriptors.
This is because the typemap calls PerlIO_findFILE(), which sometimes
(but not always) calls PerlIO_exportFILE(). To be consistent,
PerlIO_fildFILE() needs to either always give you a reference, or
always not give you a reference. It seems better to do the latter as
the call to PerlIO_exportFILE() is only an implementation detail, so
arrange for it to immediately free up the reference that
PerlIO_exportFILE() created.

p4raw-id: //depot/perl@32224