Enhanced printk() merged

Yes indeed, and printk() is marked up with the printf attribute. The trick 
is to find a way to define new format characters that doesn't cause GCC to 
warn about all of them.

There were attempts in the past to make the format attributes dynamically 
redefinable, but if I recall correctly the consensus in the end was that 
this was simply too damn complicated.

(I wonder if what we need is loose versions of the format attribute's 
archetypes, which warn about incorrect numbers of parameters and type 
mismatches for format letters GCC knows about, but does not check format 
letters that GCC doesn't know? As long as nobody tries to reimplement 
something like .* which changes the number of arguments consumed, this 
should work fine.)