Cygwin: let feraiseexcept actually raise an exception

Cygwin: let feraiseexcept actually raise an exception

The exception handling inside of Cygwin functions marked as SIGFE
covers exceptions and lets the library code handle them gracefully.
If these functions want to raise an exception, they have to send a
signal explicitely via raise(3).

That's not what we want in feraiseexcept(). It triggers a floating
point exception explicitely by calling the i387 op "fwait".  Being
marked as SIGFE, this exception will be suppressed and the normal
exception handling won't kick in.

Fix this by moving feraiseexcept into the NOSIGFE realm.

Fixes: 0f81b5d4bcaa ("* Makefile.in (DLL_OFILES): Add new fenv.o module.")
Signed-off-by: Corinna Vinschen <corinna@vinschen.de>