store: Add comments for the stracer.

* guix/store.scm (%worker-magic-1, %worker-magic-2): Add comments.

guix/store.scm

@@ -100,8 +100,8 @@ (define-module (guix store)
 
 (define %protocol-version #x10c)
 
-(define %worker-magic-1 #x6e697863)
-(define %worker-magic-2 #x6478696f)
+(define %worker-magic-1 #x6e697863)               ; "nixc"
+(define %worker-magic-2 #x6478696f)               ; "dxio"
 
 (define (protocol-major magic)
   (logand magic #xff00))