Removed misleading/unnecessary use of ImGuiButtonFlags_AllowItemOverl…

…ap in BeginSubplots(). (#203)

Likely this was pulled from SplitterBehavior(), where it made senses but only given the possibility user would call SetItemAllowOverlap() after.
AFAIK after debugging the code I _think_ this has no meaningful side-effect. Also removed same thing in Tables code in core lib.
Flag added in 4a1ee88.

implot.cpp

@@ -3397,7 +3397,7 @@ bool BeginSubplots(const char* title, int rows, int cols, const ImVec2& size, Im
  ImGui::KeepAliveID(sep_id);
  const ImRect sep_bb = ImRect(subplot.GridRect.Min.x, ypos-SUBPLOT_SPLITTER_HALF_THICKNESS, subplot.GridRect.Max.x, ypos+SUBPLOT_SPLITTER_HALF_THICKNESS);
  bool sep_hov = false, sep_hld = false;
- const bool sep_clk = ImGui::ButtonBehavior(sep_bb, sep_id, &sep_hov, &sep_hld, ImGuiButtonFlags_FlattenChildren | ImGuiButtonFlags_AllowItemOverlap | ImGuiButtonFlags_PressedOnClick | ImGuiButtonFlags_PressedOnDoubleClick);
+ const bool sep_clk = ImGui::ButtonBehavior(sep_bb, sep_id, &sep_hov, &sep_hld, ImGuiButtonFlags_FlattenChildren | ImGuiButtonFlags_PressedOnClick | ImGuiButtonFlags_PressedOnDoubleClick);
  if ((sep_hov && G.HoveredIdTimer > SUBPLOT_SPLITTER_FEEDBACK_TIMER) || sep_hld) {
  if (sep_clk && ImGui::IsMouseDoubleClicked(0)) {
  float p = (subplot.RowRatios[r] + subplot.RowRatios[r+1])/2;
@@ -3427,7 +3427,7 @@ bool BeginSubplots(const char* title, int rows, int cols, const ImVec2& size, Im
  ImGui::KeepAliveID(sep_id);
  const ImRect sep_bb = ImRect(xpos-SUBPLOT_SPLITTER_HALF_THICKNESS, subplot.GridRect.Min.y, xpos+SUBPLOT_SPLITTER_HALF_THICKNESS, subplot.GridRect.Max.y);
  bool sep_hov = false, sep_hld = false;
- const bool sep_clk = ImGui::ButtonBehavior(sep_bb, sep_id, &sep_hov, &sep_hld, ImGuiButtonFlags_FlattenChildren | ImGuiButtonFlags_AllowItemOverlap | ImGuiButtonFlags_PressedOnClick | ImGuiButtonFlags_PressedOnDoubleClick);
+ const bool sep_clk = ImGui::ButtonBehavior(sep_bb, sep_id, &sep_hov, &sep_hld, ImGuiButtonFlags_FlattenChildren | ImGuiButtonFlags_PressedOnClick | ImGuiButtonFlags_PressedOnDoubleClick);
  if ((sep_hov && G.HoveredIdTimer > SUBPLOT_SPLITTER_FEEDBACK_TIMER) || sep_hld) {
  if (sep_clk && ImGui::IsMouseDoubleClicked(0)) {
  float p = (subplot.ColRatios[c] + subplot.ColRatios[c+1])/2;