Older versions of NASM would not try to match unknown %if directives
with a corresponding %endif, resulting in some very odd consequences
when it comes to trying to handle support for multiple NASM versions.
Document the problem.
Reported-by: E. C. Masloch <pushbx@ulukai.org>
Signed-off-by: H. Peter Anvin <hpa@zytor.com>
31c4d8bcfd