Revert "make PerlIO handle FD_CLOEXEC"

This reverts commit 2cdf406af42834c46ef407517daab0734f7066fc.

The reason for the revert is that with this commit, perl fails to
compile on darwin (or at least, one some versions of it):

    ./miniperl -Ilib make_ext.pl lib/auto/DB_File/DB_File.bundle  MAKE="/Applications/Xcode.app/Contents/Developer/usr/bin/make" LIBPERL_A=libperl.a LINKTYPE=dynamic
    Parsing config.in...
    Looks Good.
    dyld: lazy symbol binding failed: Symbol not found: _mkostemp
      Referenced from: /private/tmp/perl/cpan/DB_File/../../miniperl
      Expected in: flat namespace

    dyld: Symbol not found: _mkostemp
      Referenced from: /private/tmp/perl/cpan/DB_File/../../miniperl
      Expected in: flat namespace

    Unsuccessful Makefile.PL(cpan/DB_File): code=5 at make_ext.pl line 518.
    make: *** [lib/auto/DB_File/DB_File.bundle] Error 2

1 files changed, 5 insertions, 0 deletions

diff --git a/toke.c b/toke.c
index 6e2742742a..75249430f0 100644
--- a/toke.c
+++ b/toke.c
@@ -7669,6 +7669,11 @@ Perl_yylex(pTHX)
 		if (!GvIO(gv))
 		    GvIOp(gv) = newIO();
 		IoIFP(GvIOp(gv)) = PL_rsfp;
+		{
+		    const int fd = PerlIO_fileno(PL_rsfp);
+                    if (fd >= 3)
+			setfd_cloexec(fd);
+		}
 		/* Mark this internal pseudo-handle as clean */
 		IoFLAGS(GvIOp(gv)) |= IOf_UNTAINT;
 		if ((PerlIO*)PL_rsfp == PerlIO_stdin())