Fixed to #include correct 32-bit headers; Refreshed libc/kernel headers

This patch fixes an issue where 64-bit hreaders are incorrectly included
in kernel headers.  For example, file "libc/kernel/arch-x86/asm/io.h"
incorreclty includes "io_64.h" (missing, BTW) instead of "io_32.h".

The reason is because CONFIG_X86_32 isn't considered pre-defined in
"kernel_default_arch_macros" for x86, and clean_header.py doesn't
look at it at all anyway (ie. __i386__ is also ignored, but it's
okay since x86 cross compiler defines it back)

Fixed 2 tools/*py, README.TXT, and refreshed libc/kernel headers

Change-Id: Iac834cc8b3548f055d3f2a214af36072dd679fe8
diff --git a/libc/kernel/arch-x86/asm/signal.h b/libc/kernel/arch-x86/asm/signal.h
index a15028c..1c8f2f6 100644
--- a/libc/kernel/arch-x86/asm/signal.h
+++ b/libc/kernel/arch-x86/asm/signal.h
@@ -93,35 +93,20 @@
 /* WARNING: DO NOT EDIT, AUTO-GENERATED CODE - SEE TOP FOR INSTRUCTIONS */
 #include <asm-generic/signal.h>
 #ifndef __ASSEMBLY__
-#ifdef __i386__
 struct sigaction {
-/* WARNING: DO NOT EDIT, AUTO-GENERATED CODE - SEE TOP FOR INSTRUCTIONS */
  union {
+/* WARNING: DO NOT EDIT, AUTO-GENERATED CODE - SEE TOP FOR INSTRUCTIONS */
  __sighandler_t _sa_handler;
  void (*_sa_sigaction)(int, struct siginfo *, void *);
  } _u;
-/* WARNING: DO NOT EDIT, AUTO-GENERATED CODE - SEE TOP FOR INSTRUCTIONS */
  sigset_t sa_mask;
+/* WARNING: DO NOT EDIT, AUTO-GENERATED CODE - SEE TOP FOR INSTRUCTIONS */
  unsigned long sa_flags;
  void (*sa_restorer)(void);
 };
-/* WARNING: DO NOT EDIT, AUTO-GENERATED CODE - SEE TOP FOR INSTRUCTIONS */
 #define sa_handler _u._sa_handler
+/* WARNING: DO NOT EDIT, AUTO-GENERATED CODE - SEE TOP FOR INSTRUCTIONS */
 #define sa_sigaction _u._sa_sigaction
-#else
-struct sigaction {
-/* WARNING: DO NOT EDIT, AUTO-GENERATED CODE - SEE TOP FOR INSTRUCTIONS */
- __sighandler_t sa_handler;
- unsigned long sa_flags;
- __sigrestore_t sa_restorer;
- sigset_t sa_mask;
-/* WARNING: DO NOT EDIT, AUTO-GENERATED CODE - SEE TOP FOR INSTRUCTIONS */
-};
-struct k_sigaction {
- struct sigaction sa;
-};
-/* WARNING: DO NOT EDIT, AUTO-GENERATED CODE - SEE TOP FOR INSTRUCTIONS */
-#endif
 typedef struct sigaltstack {
  void __user *ss_sp;
  int ss_flags;