replace default handler for SIGBUS
replace default handler for SIGBUS

default handler for SIGBUS print message "Bus error (core dump)".
replace the default handler and print message more friendly.

this is a temporary patch.
in the long term, we plan to modify the code from "void" return
type to "int" type, for memcpy_to_gas/memcpy_from_gas etc.
once these functions have return value to signify its success
or fail to the client, the async method of raise signal could be
avoided.

Microsemi/switchtec-user,Microsemi/switchtec-user