fail/core/plugins/tracing

Some hints on memory-access tracing in Bochs:
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 - Instruction fetches: no memory accesses!
 - INC ${MEM_ADDR} (increment in memory): a read and a write access
 - CALL ${INSTR_ADDR} (call function): a single write access
 - PUSH %{REG} (push on stack): dito
 - PUSHF (push on stack): dito
 - INT ${INTERRUPT#} (interrupt trigger): 3 write accesses