Solving issue 1684: "thumbnail.cc uses Glib::Mutex recusively" ; this changeset introduce a new MyMutex and MyMutex::MyLock class that has to be used instead of Glib ones

rtengine/image8.h

@@ -46,7 +46,7 @@ class Image8 : public IImage8, public ImageIO {
         virtual void         setScanline (int row, unsigned char* buffer, int bps, float *minValue=NULL, float *maxValue=NULL);
 
         // functions inherited from IImage*:
-        virtual Glib::Mutex& getMutex () { return mutex (); }
+        virtual MyMutex&     getMutex () { return mutex (); }
         virtual cmsHPROFILE  getProfile () { return getEmbeddedProfile (); }
         virtual int          getBitsPerPixel () { return 8*sizeof(unsigned char); }
         virtual int          saveToFile (Glib::ustring fname) { return save (fname); }