Force erroneous inclusions of compiler-*.h files to be errors

Replace worthless comments with actual preprocessor errors when including
the wrong versions of the compiler.h files.

[[e-mail]: make it work]
Signed-off-by: Robert P. J. Day <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
Signed-off-by: Linus Torvalds <[e-mail]>

include/linux/compiler-gcc.h

···
-/* Never include this file directly.  Include <linux/compiler.h> instead.  */
+#ifndef __LINUX_COMPILER_H
+#error "Please don't include <linux/compiler-gcc.h> directly, include <linux/compiler.h> instead."
+#endif
 
 /*
  * Common definitions for all gcc versions go here.

include/linux/compiler-gcc3.h

···
-/* Never include this file directly.  Include <linux/compiler.h> instead.  */
+#ifndef __LINUX_COMPILER_H
+#error "Please don't include <linux/compiler-gcc3.h> directly, include <linux/compiler.h> instead."
+#endif
 
 /* These definitions are for GCC v3.x.  */
 #include <linux/compiler-gcc.h>

include/linux/compiler-gcc4.h

···
-/* Never include this file directly.  Include <linux/compiler.h> instead.  */
+#ifndef __LINUX_COMPILER_H
+#error "Please don't include <linux/compiler-gcc4.h> directly, include <linux/compiler.h> instead."
+#endif
 
 /* These definitions are for GCC v4.x.  */
 #include <linux/compiler-gcc.h>

include/linux/compiler-intel.h

···
-/* Never include this file directly.  Include <linux/compiler.h> instead.  */
+#ifndef __LINUX_COMPILER_H
+#error "Please don't include <linux/compiler-intel.h> directly, include <linux/compiler.h> instead."
+#endif
 
 #ifdef __ECC