Port to strict C99 offsetof

* src/bidi.c (bidi_copy_it):
* src/lisp.h (CHAR_TABLE_EXTRA_SLOTS):
Use only a single identifier as the second argument of offsetof.
Found by using clang -pedantic.

src/bidi.c

@@ -532,7 +532,7 @@ bidi_copy_it (struct bidi_it *to, struct bidi_it *from)
   /* Copy everything from the start through the active part of
      the level stack.  */
   memcpy (to, from,
-	  (offsetof (struct bidi_it, level_stack[1])
+	  (offsetof (struct bidi_it, level_stack) + sizeof from->level_stack[0]
 	   + from->stack_idx * sizeof from->level_stack[0]));
 }
 

src/lisp.h

@@ -1766,7 +1766,8 @@ CHAR_TABLE_EXTRA_SLOTS (struct Lisp_Char_Table *ct)
 
 /* Make sure that sub char-table contents slot is where we think it is.  */
 verify (offsetof (struct Lisp_Sub_Char_Table, contents)
-	== offsetof (struct Lisp_Vector, contents[SUB_CHAR_TABLE_OFFSET]));
+	== (offsetof (struct Lisp_Vector, contents)
+	    + SUB_CHAR_TABLE_OFFSET * sizeof (Lisp_Object)));
 
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