autoconf: use -std=c17 or -std=c11 if available
autoconf: use -std=c17 or -std=c11 if available

If the compiler supports it, use -std=c17 or -std=c11. Hopefully, this
will give us more predictable behavior in some cases.

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

techkey/nasm,techkey/nasm,techkey/nasm,techkey/nasm,techkey/nasm