Add x86_64 to the bionic headers.

Manual changes:

  cpp.py: cope with macros that refer to other macros.

  defaults.py: x86 no longer always implies __i386__; use __i386__ to replace
  the kernel CONFIG_X86_32 flag.

  asm/page.h: the upstream page.h isn't a uapi header and no longer includes
  the stuff we were using it for. Let's just have our own static file, since
  it's the same for all our architectures (both 32- and 64-bit).

  sys/select.h: we used to use the various FD_SET-related macros from the
  kernel header files, but they've gone. Adjust by adding trivial equivalent
  definitions.

Automated changes:

  libc/kernel/arch-x86, libc/kernel/common: regenerated from
  external/kernel-headers.

Change-Id: I84fc0ed52dc742e043b4ae300fd3b58ee99b7fcd
diff --git a/libc/kernel/arch-x86/asm/msgbuf.h b/libc/kernel/arch-x86/asm/msgbuf.h
index 99caf76..7580210 100644
--- a/libc/kernel/arch-x86/asm/msgbuf.h
+++ b/libc/kernel/arch-x86/asm/msgbuf.h
@@ -22,20 +22,28 @@
  struct ipc64_perm msg_perm;
 /* WARNING: DO NOT EDIT, AUTO-GENERATED CODE - SEE TOP FOR INSTRUCTIONS */
  __kernel_time_t msg_stime;
+#ifdef __i386__
  unsigned long __unused1;
+#endif
+/* WARNING: DO NOT EDIT, AUTO-GENERATED CODE - SEE TOP FOR INSTRUCTIONS */
  __kernel_time_t msg_rtime;
+#ifdef __i386__
  unsigned long __unused2;
+#endif
 /* WARNING: DO NOT EDIT, AUTO-GENERATED CODE - SEE TOP FOR INSTRUCTIONS */
  __kernel_time_t msg_ctime;
+#ifdef __i386__
  unsigned long __unused3;
+#endif
+/* WARNING: DO NOT EDIT, AUTO-GENERATED CODE - SEE TOP FOR INSTRUCTIONS */
  unsigned long msg_cbytes;
  unsigned long msg_qnum;
-/* WARNING: DO NOT EDIT, AUTO-GENERATED CODE - SEE TOP FOR INSTRUCTIONS */
  unsigned long msg_qbytes;
  __kernel_pid_t msg_lspid;
+/* WARNING: DO NOT EDIT, AUTO-GENERATED CODE - SEE TOP FOR INSTRUCTIONS */
  __kernel_pid_t msg_lrpid;
  unsigned long __unused4;
-/* WARNING: DO NOT EDIT, AUTO-GENERATED CODE - SEE TOP FOR INSTRUCTIONS */
  unsigned long __unused5;
 };
+/* WARNING: DO NOT EDIT, AUTO-GENERATED CODE - SEE TOP FOR INSTRUCTIONS */
 #endif