Fixup: build under linux 4.14 (#581)

Split compiler_types.h from compiler.h only available for linux 4.14

kernel/allowlist.c

@@ -1,6 +1,5 @@
 #include "ksu.h"
 #include "linux/compiler.h"
-#include "linux/compiler_types.h"
 #include "linux/fs.h"
 #include "linux/gfp.h"
 #include "linux/kernel.h"
@@ -8,6 +7,10 @@
 #include "linux/printk.h"
 #include "linux/slab.h"
 #include "linux/version.h"
+#if LINUX_VERSION_CODE >= KERNEL_VERSION(4, 14, 0)
+#include "linux/compiler_types.h"
+#endif
+
 #include "klog.h" // IWYU pragma: keep
 #include "selinux/selinux.h"
 #include "kernel_compat.h"
@@ -377,4 +380,4 @@ void ksu_allowlist_exit(void)
 		kfree(np);
 	}
 	mutex_unlock(&allowlist_mutex);
-}
+}