1.0.1.17: Remove Win32 exception trampolines

  Remove context-restore trap.
  Remove sigtrap_trampoline and exception_trampoline, sigtrap_emulator,
    sigtrap_wrapper, and handle_win32_exception_wrapper.
  Change handle_exception to call HANDLE-WIN32-EXCEPTION and
    sigtrap_wrapper directly.
  Remove the saved context and exception from the SEH frame structure.