NetBSD defines ELF_ST_TYPE

NetBSD 4.0 defines ELF_ST_TYPE and ELF_ST_BIND already, so these definitions for x86_64 in rts/Linker.c should be conditional on non-existence,as they are for i386, not just conditional on not-FreeBSD.

--- rts/Linker.c.dist   2008-06-03 10:21:22.000000000 -0700
+++ rts/Linker.c        2008-06-05 17:01:11.000000000 -0700
@@ -2612,10 +2612,16 @@
 #define Elf_Sym     Elf64_Sym
 #define Elf_Rel     Elf64_Rel
 #define Elf_Rela    Elf64_Rela
-#if !defined(freebsd_HOST_OS)
+#ifndef ELF_ST_TYPE
 #define ELF_ST_TYPE ELF64_ST_TYPE
+#endif
+#ifndef ELF_ST_BIND
 #define ELF_ST_BIND ELF64_ST_BIND
+#endif
+#ifndef ELF_R_TYPE
 #define ELF_R_TYPE  ELF64_R_TYPE
+#endif
+#ifndef ELF_R_SYM
 #define ELF_R_SYM   ELF64_R_SYM
 #endif
 #else