patch 7.4.1869
Problem: Can't build with old version of Perl.
Solution: Define PERLIO_FUNCS_DECL. (Tom G. Christensen)
diff --git a/src/if_perl.xs b/src/if_perl.xs
index a489994..83f1479 100644
--- a/src/if_perl.xs
+++ b/src/if_perl.xs
@@ -61,6 +61,17 @@
# include <perliol.h>
#endif
+/* Workaround for perl < 5.8.7 */
+#ifndef PERLIO_FUNCS_DECL
+# ifdef PERLIO_FUNCS_CONST
+# define PERLIO_FUNCS_DECL(funcs) const PerlIO_funcs funcs
+# define PERLIO_FUNCS_CAST(funcs) (PerlIO_funcs*)(funcs)
+# else
+# define PERLIO_FUNCS_DECL(funcs) PerlIO_funcs funcs
+# define PERLIO_FUNCS_CAST(funcs) (funcs)
+# endif
+#endif
+
/*
* Work around clashes between Perl and Vim namespace. proto.h doesn't
* include if_perl.pro and perlsfio.pro when IN_PERL_FILE is defined, because