Deprecate MMCore ImageSynchro functions

Among other things, it doesn't even do what it says because it only
applies to snap, not to sequence acquisition.

ImageSynchro has not been used by MMStudio for a long time.

Apps can simply wait for individual devices as needed.

MMCore/MMCore.cpp

@@ -1316,6 +1316,8 @@ void CMMCore::waitForConfig(const char* group, const char* configName) throw (CM
 
 /**
  * Wait for the slowest device in the ImageSynchro list.
+ *
+ * @deprecated ImageSynchro will not be supported in the future.
  */
 void CMMCore::waitForImageSynchro() throw (CMMError)
 {
@@ -2469,6 +2471,8 @@ namespace
  * Add device to the image-synchro list. Image acquisition waits for all devices
  * in this list.
  * @param label   the device label
+ *
+ * @deprecated ImageSynchro will not be supported in the future.
  */
 void CMMCore::assignImageSynchro(const char* label) throw (CMMError)
 {
@@ -2485,6 +2489,8 @@ void CMMCore::assignImageSynchro(const char* label) throw (CMMError)
 /**
  * Removes device from the image-synchro list.
  * @param label   the device label
+ *
+ * @deprecated ImageSynchro will not be supported in the future.
  */
 void CMMCore::removeImageSynchro(const char* label) throw (CMMError)
 {
@@ -2497,6 +2503,8 @@ void CMMCore::removeImageSynchro(const char* label) throw (CMMError)
 
 /**
  * Clears the image synchro device list.
+ *
+ * @deprecated ImageSynchro will not be supported in the future.
  */
 void CMMCore::removeImageSynchroAll()
 {

MMCore/MMCore.h

@@ -242,7 +242,7 @@ class CMMCore
    void waitForConfig(const char* group, const char* configName) throw (CMMError);
    bool systemBusy() throw (CMMError);
    void waitForSystem() throw (CMMError);
-   void waitForImageSynchro() throw (CMMError);
+   MMCORE_DEPRECATED(void waitForImageSynchro() throw (CMMError));
    bool deviceTypeBusy(MM::DeviceType devType) throw (CMMError);
    void waitForDeviceType(MM::DeviceType devType) throw (CMMError);
 
@@ -386,9 +386,9 @@ class CMMCore
    std::string getCameraChannelName(unsigned int channelNr);
    long getImageBufferSize();
 
-   void assignImageSynchro(const char* deviceLabel) throw (CMMError);
-   void removeImageSynchro(const char* deviceLabel) throw (CMMError);
-   void removeImageSynchroAll();
+   MMCORE_DEPRECATED(void assignImageSynchro(const char* deviceLabel) throw (CMMError));
+   MMCORE_DEPRECATED(void removeImageSynchro(const char* deviceLabel) throw (CMMError));
+   MMCORE_DEPRECATED(void removeImageSynchroAll());
 
    void setAutoShutter(bool state);
    bool getAutoShutter();