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

kernel/system/do_safecopy.c

@@ -16,7 +16,7 @@
 #include <assert.h>
 
 #include "kernel/system.h"
-#include "kernel.h"
+#include "kernel/kernel.h"
 
 #define MAX_INDIRECT_DEPTH 5	/* up to how many indirect grants to follow? */
 

kernel/system/do_safememset.c

@@ -13,7 +13,7 @@
 #include <minix/safecopies.h>
 
 #include "kernel/system.h"
-#include "kernel.h"
+#include "kernel/kernel.h"
 
 /*===========================================================================*
  *                              do_safememset                                *

kernel/system/do_sprofile.c

@@ -14,7 +14,7 @@
  */
 
 #include "kernel/system.h"
-#include "watchdog.h"
+#include "kernel/watchdog.h"
 
 #if SPROFILE