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

libc/kernel/tools/defaults.py

@@ -44,7 +44,7 @@ kernel_remove_config_macros = True
 # toolchain preprocessor
 kernel_default_arch_macros = {
     "arm": {},
-    "x86": {"__i386__": "1"},
+    "x86": {"__i386__": "1", "CONFIG_X86_32": "1"},
     }
 
 # Replace tokens in the output according to this mapping