[S390] use siginfo for sigtrap signals

Provide additional information on SIGTRAP by using a sig_info signal.
Use TRAP_BRKPT for breakpoints via illegal operation and TRAP_HWBKPT
for breakpoints via program event recording. Provide the address of
the instruction that caused the breakpoint via si_addr.
While we are at it get rid of tracehook_consider_fatal_signal.

Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>