Clipper: further mitigation/improvements for abnormally large contents ranges (larger than e.g. 2^31). (#3609, #8215)

imgui.h

@@ -2708,7 +2708,7 @@ struct ImGuiListClipper
     int             DisplayEnd;         // End of items to display (exclusive)
     int             ItemsCount;         // [Internal] Number of items
     float           ItemsHeight;        // [Internal] Height of item after a first step and item submission can calculate it
-    float           StartPosY;          // [Internal] Cursor position at the time of Begin() or after table frozen rows are all processed
+    double          StartPosY;          // [Internal] Cursor position at the time of Begin() or after table frozen rows are all processed
     double          StartSeekOffsetY;   // [Internal] Account for frozen rows in a table and initial loss of precision in very large windows.
     void*           TempData;           // [Internal] Internal data