eina - mmap safety handler - fix to only handle sigbus's from io

eina - mmap safety handler - fix to only handle sigbus's from io

@fix

this fixes the eina mmap safety handler to only  handle what comes
from actual i/o errors (not actual corrupt/hw memory faults or invalid
objects), and if it's not a sigbus eina mmap should handle then pass
it onto the previous handler before eina mmap took over.