Stop using deprecated Core callback functions

[marktsuchida]

Following #710 and #715, these functions in MMDevice's MM::Core are slated for removal but are still being used. This issue is a reminder to eventually remove them.

MM_DEPRECATED(virtual int GetFocusPosition(double& pos)) = 0;
MM_DEPRECATED(virtual MM::SignalIO* GetSignalIODevice(const MM::Device* caller, const char* deviceName)) = 0;

mmCoreAndDevices/DeviceAdapters/FakeCamera/FakeCamera.cpp

Line 461 in b7d5816

if (GetCoreCallback()->GetFocusPosition(val) != 0)

mmCoreAndDevices/DeviceAdapters/TwoPhoton/VirtualShutter.cpp

Lines 115 to 186 in b7d5816

	int VirtualShutter::SetOpen(bool open) {
	char dev1[MM::MaxStrLength];
	GetProperty(g_PropertyDev1, dev1);
	char dev2[MM::MaxStrLength];
	GetProperty(g_PropertyDev2, dev2);
	if (strlen(dev1) > 0)
	{
	MM::SignalIO* pDev1 = GetCoreCallback()->GetSignalIODevice(this, dev1);
	int ret = pDev1->SetGateOpen(open);
	if (ret != DEVICE_OK)
	return ret;
	}
	if (strlen(dev2) > 0)
	{
	MM::SignalIO* pDev2 = GetCoreCallback()->GetSignalIODevice(this, dev2);
	int ret = pDev2->SetGateOpen(open);
	if (ret != DEVICE_OK)
	return ret;
	}
	return DEVICE_OK;
	}
	int VirtualShutter::GetOpen(bool& open) {
	char dev1[MM::MaxStrLength];
	GetProperty(g_PropertyDev1, dev1);
	char dev2[MM::MaxStrLength];
	GetProperty(g_PropertyDev2, dev2);
	bool open1(false);
	if (strlen(dev1) > 0)
	{
	MM::SignalIO* pDev1 = GetCoreCallback()->GetSignalIODevice(this, dev1);
	if (pDev1)
	{
	int ret = pDev1->GetGateOpen(open1);
	if (ret != DEVICE_OK)
	return ret;
	}
	else
	return ERR_UNKNOWN_DA_DEVICE;
	}
	bool open2;
	if (strlen(dev2) > 0)
	{
	MM::SignalIO* pDev2 = GetCoreCallback()->GetSignalIODevice(this, dev2);
	if (pDev2)
	{
	int ret = pDev2->GetGateOpen(open2);
	if (ret != DEVICE_OK)
	return ret;
	}
	else
	return ERR_UNKNOWN_DA_DEVICE;
	}
	else
	open2 = open1;
	assert(open1 == open2);
	open = open1;
	return DEVICE_OK;
	}

TwoPhoton is (as I understand) long unmaintained, so the answer might be to remove it. Not yet sure what the best solution is for FakeCamera.