This happens with functions that aren't intended to return e.g. like
_Unwind_Resume. In these cases, the return address is outside of the
function (the first instruction in the next function).

Set the flag CONTEXT_UNWOUND_TO_CALL after unwinding to a callsite,
and if this flag is set, look up a RUNTIME_FUNCTION based on
Control.Pc - 4.

This isn't a complete (nor probably entirely correct) implementation
of the flag CONTEXT_UNWOUND_TO_CALL, but it practically seems to
work fine and fixes a large number of unwinding cases.
Signed-off-by: Martin Storsjo <martin@martin.st>
Signed-off-by: Alexandre Julliard <julliard@winehq.org>