[GCC 3.0] New -Wall warnings without corresponding option to turn off

[Marc Espie]

At least two such warnings are a problem:
/spare/src/sys/arch/i386/isa/npx.c:155:6: multi-line string literals are
deprecated
/spare/src/sys/net/if_loop.c:300:8: extra tokens at end of #endif directive


Those are rather common practice, and some fairly important programs do
use -Wall -Werror.

Not being able to have -Wall -Wdisable-those -Werror is a significant
usability regression from 2.95.3.