Clear the floating point exception flag before returning to
user space. This is needed, else the libc trampoline handler
may hit the same SIGFPE again while building up a trampoline
to a signal handler.

Fixes debian bug #559406.
Signed-off-by: Helge Deller <deller@gmx.de>
Signed-off-by: Kyle McMartin <kyle@mcmartin.ca>