do not catch SIGBUS either as per SIG35-C

This related to commit: 2bef62a7561ccca8509a4ceaaf471967c5737fb6
SIGBUS is also in the list of Signals that should not be cought. see:
https://www.securecoding.cert.org/confluence/display/seccode/SIG35-C.+Do
+not+return+from+a+computational+exception+signal+handler
Merge branch 'vvatsa/master'
Only handle all signals if the ipc semaphore is used (Issue #98)