changes.src: slighly better description of new instructions
changes.src: slighly better description of new instructions

Describe what the new instructions actually are.

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

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