It is extremely desirable to allow the user fine-grained control of
warnings, but this has been complicated by the fact that a warning
class has had to be defined in no less than three places (error.h,
error.c, nasmdoc.src) before it can be used in source code. Instead,
use a script to define these via magic comments at the point of use.
This hopefully will encourage creating new classes as needed.
Signed-off-by: H. Peter Anvin (Intel) <hpa@zytor.com>