compiler.h: add offsetof() and container_of()
compiler.h: add offsetof() and container_of()

offsetof() is a C99 construct; provided here as an ersatz for older
systems.

container_of() is a nonstandard but highly useful construct, which
allows data structure control items like tree structures to be
embedded in larger data structures without the penalty of extra
pointers and allocations.

Signed-off-by: H. Peter Anvin <8a453bad9912ffe59bc0f0b8abe03df9be19379e@zytor.com>

techkey/nasm,turingstudio/nasm,letolabs/nasm,projedi/nasm,letolabs/nasm,techkey/nasm,Distrotech/nasm,projedi/nasm,Distrotech/nasm,turingstudio/nasm,letolabs/nasm,turingstudio/nasm,techkey/nasm,Distrotech/nasm,projedi/nasm,Distrotech/nasm,projedi/nasm,projedi/nasm,techkey/nasm,techkey/nasm,turingstudio/nasm