- the signal trampoline address is given to the kernel by a sigaction()
fourth argument
- we introduce an irix_emuldata structure to keep track of the signal
trampoline address
- we don't support per-sigaction signal trampolines, we only do per-process
- now that we use the IRIX libc signal trampoline, we do not have to handle
the errno update from the signal trampoline
- it is possible that IRIX 5 signal delivery works too, since theses binaries
will come with their own signal trampoline