Add missing arch-specific AT_ cruft.

AP_FPUCW is referenced by valgrind.

Bug: https://bugs.kde.org/show_bug.cgi?id=339945
Test: valgrind builds with one less hack
Change-Id: I7146f3709286662108cc82ba3c55ce935375a1f1
diff --git a/libc/include/elf.h b/libc/include/elf.h
index 2950e0a..28f3c3b 100644
--- a/libc/include/elf.h
+++ b/libc/include/elf.h
@@ -31,7 +31,7 @@
 
 #include <sys/cdefs.h>
 
-#include <linux/auxvec.h>
+#include <bits/auxvec.h>
 #include <linux/elf.h>
 #include <linux/elf-em.h>
 #include <machine/elf_machdep.h>