x86, setup: move isdigit.h to ctype.h, header files on top.

It is a subset of <ctype.h> functionality, so name it ctype.h.  Also,
reorganize header files so #include statements are clustered near the
top as they should be.

Signed-off-by: H. Peter Anvin <hpa@zytor.com>
LKML-Reference: <4C5752F2.8030206@kernel.org>
diff --git a/arch/x86/boot/boot.h b/arch/x86/boot/boot.h
index 00cf51c..c7093bd 100644
--- a/arch/x86/boot/boot.h
+++ b/arch/x86/boot/boot.h
@@ -28,6 +28,7 @@
 #include "bitops.h"
 #include <asm/cpufeature.h>
 #include <asm/processor-flags.h>
+#include "ctype.h"
 
 /* Useful macros */
 #define BUILD_BUG_ON(condition) ((void)sizeof(char[1 - 2*!!(condition)]))
@@ -200,8 +201,6 @@
 	return diff;
 }
 
-#include "isdigit.h"
-
 /* Heap -- available for dynamic lists. */
 extern char _end[];
 extern char *HEAP;