: 2. Is this extension sanctioned by ansi, or will it be in the future?

Already standardized in c99.  Gnu has its own, different varadic
extensions, but also supports those defined in c99.

: 3. Do we want to make it easier or more difficult to compile kernels with
:    a non-gcc compiler?

Most ANSI compilers already support varadic macros.  FreeBSD's kernel
can compile with intel's icc, for example.

Warner