fix switch statement in signal.c

[Chris Faylor]

On Mon, Sep 18, 2000 at 11:03:19PM -0700, Geoff Keating wrote:
>I didn't know that you weren't allowed to do this, and apparently the
>authors of signal.c didn't either, but Mark Mitchell does know and he
>just committed some substantial changes to the GCC C frontend that
>included this check.
>
>(SIG_DFL and similar are #defined to be like (void (*)(int))-2
>which is not an 'integral constant expression'.)

Whether it is correct or not, this change sounds like it has the
capacity to create a lot of confusion.

cgf