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/arch/i386/kernel.lds

@@ -33,4 +33,5 @@ SECTIONS
 		__k_unpaged__kern_size = . - _kern_vir_base;
 		_kern_size = __k_unpaged__kern_size;
 	}
+	_end = .;
 }