style: rename drag functions argument held to out_held in header (#641)

Modifies implot.h DragPoint, DragLineX, DragLineY, DragRect functions held argument to out_held.
The last parameter is called out_held in the implementation cpp file.
This change brings that to the header, provides clearer understanding for the user.

Co-authored-by: Breno Cunha Queiroz <brenocq.br@gmail.com>

Author: mihaly-sisak

implot.h

@@ -938,13 +938,13 @@ IMPLOT_API void PlotDummy(const char* label_id, ImPlotDummyFlags flags=0);
 // user interactions can be retrieved through the optional output parameters.
 
 // Shows a draggable point at x,y. #col defaults to ImGuiCol_Text.
-IMPLOT_API bool DragPoint(int id, double* x, double* y, const ImVec4& col, float size = 4, ImPlotDragToolFlags flags = 0, bool* out_clicked = nullptr, bool* out_hovered = nullptr, bool* held = nullptr);
+IMPLOT_API bool DragPoint(int id, double* x, double* y, const ImVec4& col, float size = 4, ImPlotDragToolFlags flags = 0, bool* out_clicked = nullptr, bool* out_hovered = nullptr, bool* out_held = nullptr);
 // Shows a draggable vertical guide line at an x-value. #col defaults to ImGuiCol_Text.
-IMPLOT_API bool DragLineX(int id, double* x, const ImVec4& col, float thickness = 1, ImPlotDragToolFlags flags = 0, bool* out_clicked = nullptr, bool* out_hovered = nullptr, bool* held = nullptr);
+IMPLOT_API bool DragLineX(int id, double* x, const ImVec4& col, float thickness = 1, ImPlotDragToolFlags flags = 0, bool* out_clicked = nullptr, bool* out_hovered = nullptr, bool* out_held = nullptr);
 // Shows a draggable horizontal guide line at a y-value. #col defaults to ImGuiCol_Text.
-IMPLOT_API bool DragLineY(int id, double* y, const ImVec4& col, float thickness = 1, ImPlotDragToolFlags flags = 0, bool* out_clicked = nullptr, bool* out_hovered = nullptr, bool* held = nullptr);
+IMPLOT_API bool DragLineY(int id, double* y, const ImVec4& col, float thickness = 1, ImPlotDragToolFlags flags = 0, bool* out_clicked = nullptr, bool* out_hovered = nullptr, bool* out_held = nullptr);
 // Shows a draggable and resizeable rectangle.
-IMPLOT_API bool DragRect(int id, double* x1, double* y1, double* x2, double* y2, const ImVec4& col, ImPlotDragToolFlags flags = 0, bool* out_clicked = nullptr, bool* out_hovered = nullptr, bool* held = nullptr);
+IMPLOT_API bool DragRect(int id, double* x1, double* y1, double* x2, double* y2, const ImVec4& col, ImPlotDragToolFlags flags = 0, bool* out_clicked = nullptr, bool* out_hovered = nullptr, bool* out_held = nullptr);
 
 // Shows an annotation callout at a chosen point. Clamping keeps annotations in the plot area. Annotations are always rendered on top.
 IMPLOT_API void Annotation(double x, double y, const ImVec4& col, const ImVec2& pix_offset, bool clamp, bool round = false);