process.c (rb_f_system): cleanup to use rb_execarg_get

TypedData_* macros hide assignments and are confusing and too
long for users of giant fonts.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@66156 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

process.c

@@ -4445,7 +4445,7 @@ rb_f_system(int argc, VALUE *argv)
     int exec_errnum;
 
     execarg_obj = rb_execarg_new(argc, argv, TRUE, TRUE);
-    TypedData_Get_Struct(execarg_obj, struct rb_execarg, &exec_arg_data_type, eargp);
+    eargp = rb_execarg_get(execarg_obj);
     w->ec = GET_EC();
     waitpid_state_init(w, 0, 0);
     eargp->waitpid_state = w;