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

lib/libc/stdlib/putenv.c

@@ -51,6 +51,9 @@ __RCSID("$NetBSD: putenv.c,v 1.19 2010/11/14 18:11:43 tron Exp $");
 
 #ifdef __weak_alias
 __weak_alias(putenv,_putenv)
+#if defined(__minix)
+__weak_alias(__putenv50,_putenv)
+#endif /* defined(__minix) */
 #endif
 
 int