Consistently use __sun to identify SunOS

The core mostly used __sun already, but '__sun__' and 'sun' were
also present.

1 files changed, 1 insertions, 1 deletions

diff --git a/perlio.c b/perlio.c
index 46933662b0..2591f89ce9 100644
--- a/perlio.c
+++ b/perlio.c
@@ -3169,7 +3169,7 @@ PerlIOStdio_invalidate_fileno(pTHX_ FILE *f)
      */	
     f->_fileno = -1;
     return 1;
-#  elif defined(__sun__)
+#  elif defined(__sun)
     PERL_UNUSED_ARG(f);
     return 0;
 #  elif defined(__hpux)