errors: unify nasm_verror_{gnu,vc} and remove some ERR_NOFILE
errors: unify nasm_verror_{gnu,vc} and remove some ERR_NOFILE

The differences between nasm_verror_{gnu,vc} are a short handful of
strings, so unify them. Remove some additional ERR_NOFILE that are not
necessary.

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

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