It's needed by GCC2 stdc++, but we shouldn't be including it
for all consumers of <stdio.h>, which we were. Drop it,
and adjust all the things that were relying on <stdio_pre.h>'s
definition of __PRINTFLIKE to use the _PRINTFLIKE defined
in BeBuild.h instead.
Hopefully should not cause any breakage; the libroot
implementation of __freading depended on this, but
I didn't see anything else which did.