Libraries updates and cleanup

* Updating common/lib
 * Updating lib/csu
 * Updating lib/libc
 * Updating libexec/ld.elf_so
 * Corrected test on __minix in featuretest to actually follow the
   meaning of the comment.
 * Cleaned up _REENTRANT-related defintions.
 * Disabled -D_REENTRANT for libfetch
 * Removing some unneeded __NBSD_LIBC defines and tests

Change-Id: Ic1394baef74d11b9f86b312f5ff4bbc3cbf72ce2

common/lib/libc/string/explicit_bzero.c

@@ -0,0 +1,22 @@
+/* $NetBSD: explicit_bzero.c,v 1.1 2012/08/30 12:16:49 drochner Exp $ */
+
+#if !defined(_KERNEL) && !defined(_STANDALONE)
+#include <string.h>
+#define explicit_bzero __explicit_bzero
+#define explicit_memset_impl __explicit_memset_impl
+#else
+#include <lib/libkern/libkern.h>
+#endif
+
+/*
+ * The use of a volatile pointer guarantees that the compiler
+ * will not optimise the call away.
+ */
+void *(* volatile explicit_memset_impl)(void *, int, size_t) = memset;
+
+void
+explicit_bzero(void *b, size_t len)
+{
+
+	(*explicit_memset_impl)(b, 0, len);
+}