This fixes unwinding through RtlRaiseException and
call_consolidate_callback in PE builds.

Adjust the call_consolidate_callback function to store the whole
context on the stack, and use the seh "context" opcode for
unwinding to that context instead of the parent. Adjust the dwarf
escape codes for reading from the context on the stack.
Signed-off-by: Martin Storsjo <martin@martin.st>
Signed-off-by: Alexandre Julliard <julliard@winehq.org>