[PATCH] generalise net_ratelimit (printk_ratelimit)

[PATCH] generalise net_ratelimit (printk_ratelimit)

From: Anton Blanchard <anton@samba.org>

Generate a global printk rate-limiting function, printk_ratelimit().

Also, use it in the page allocator warning code.  Also add a dump_stack to
that code.

Later, we need to switch net_ratelimit() over to use printk_ratelimit().