b) give the union a name (breaks any reference to timer_list->func in C code):

 +       union {
 +               void            (*func)(struct timer_list *timer);
 +               void            (*function)(unsigned long);
 +       } u;

I'll look into that, as it seems a lot safer, and places outside
the timer code shouldn't really touch it (although I bet they do,
so more fixes for this series..)

I fear this breaks lockdep output, which turns the name of
the timer into a string that gets printed later. It should work
when these are macros, or a macro wrapping an inline function
like __init_timer is.

Ok, I'll fix it up.  Although this macro mess isn't really readable
at all.