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/usermapped_data.c

@@ -1,4 +1,4 @@
-#include "kernel.h"
+#include "kernel/kernel.h"
 
 /* This is the user-visible struct that has pointers to other bits of data. */
 struct minix_kerninfo minix_kerninfo;