Rework color marker internals to facilitate arbitrary override using SetNextItemColorMarker().

Amend fa4b47c

imgui.h

@@ -1927,12 +1927,8 @@ enum ImGuiSliderFlags_
     ImGuiSliderFlags_ClampOnInput       = 1 << 9,       // Clamp value to min/max bounds when input manually with Ctrl+Click. By default Ctrl+Click allows going out of bounds.
     ImGuiSliderFlags_ClampZeroRange     = 1 << 10,      // Clamp even if min==max==0.0f. Otherwise due to legacy reason DragXXX functions don't clamp with those values. When your clamping limits are dynamic you almost always want to use it.
     ImGuiSliderFlags_NoSpeedTweaks      = 1 << 11,      // Disable keyboard modifiers altering tweak speed. Useful if you want to alter tweak speed yourself based on your own logic.
-    ImGuiSliderFlags_AlwaysClamp        = ImGuiSliderFlags_ClampOnInput | ImGuiSliderFlags_ClampZeroRange,
-
-    // Color Markers
     ImGuiSliderFlags_ColorMarkers       = 1 << 12,      // DragScalarN(), SliderScalarN(): Draw R/G/B/A color markers on each component.
-    ImGuiSliderFlags_ColorMarkersIndexShift_ = 13,      // [Internal] DragScalar(), SliderScalar(): Pass ([0..3] << ImGuiSliderFlags_ColorMarkersIndexShift_) along with ImGuiSliderFlags_ColorMarkers to select an individual R/G/B/A color.
-
+    ImGuiSliderFlags_AlwaysClamp        = ImGuiSliderFlags_ClampOnInput | ImGuiSliderFlags_ClampZeroRange,
     ImGuiSliderFlags_InvalidMask_       = 0x7000000F,   // [Internal] We treat using those bits as being potentially a 'float power' argument from legacy API (obsoleted 2020-08) that has got miscast to this enum, and will trigger an assert if needed.
 };