[PATCH] Fix -Os related -Werror failures.

[Paul Eggert]

Jeff Law wrote:
> I would caution against blindly using 0 as an initializer.

Yes, in Emacs we use 0 only when the value does not matter so all values are 
equally "safe". It's merely a convenience to use 0, as 0 is valid for pointers 
as well as for numbers so we can use the same macro for both. We're just trying 
to pacify GCC when warnings are enabled when developing; typically in production 
warnings are disabled and there is no initializer at all.