(calling a __dead2 function such as panic() at the end of a function), the
saved %eip on the stack will actually not be part of the function that
executed a call instruction but instead will be the first instruction of
the next function in the text. This happens with dblfault_handler() and
syscall() for example. Work around this in the one place it matters by
looking at the saved %eip - 1 to determine the calling function when we
check for "magic" frames.
MFC after: 2 weeks
9819b0d8b7