Fixed some compile warnings with Clang on Windows (#3754)

backends/imgui_impl_win32.cpp

@@ -272,7 +272,7 @@ static void ImGui_ImplWin32_UpdateGamepads()
 
 static BOOL CALLBACK ImGui_ImplWin32_UpdateMonitors_EnumFunc(HMONITOR monitor, HDC, LPRECT, LPARAM)
 {
-    MONITORINFO info = { 0 };
+    MONITORINFO info = {};
     info.cbSize = sizeof(MONITORINFO);
     if (!::GetMonitorInfo(monitor, &info))
         return TRUE;

imgui.cpp

@@ -7696,6 +7696,7 @@ static void ImGui::ErrorCheckNewFrameSanityChecks()
         for (int monitor_n = 0; monitor_n < g.PlatformIO.Monitors.Size; monitor_n++)
         {
             ImGuiPlatformMonitor& mon = g.PlatformIO.Monitors[monitor_n];
+            IM_UNUSED(mon);
             IM_ASSERT(mon.MainSize.x > 0.0f && mon.MainSize.y > 0.0f && "Monitor main bounds not setup properly.");
             IM_ASSERT(ImRect(mon.MainPos, mon.MainPos + mon.MainSize).Contains(ImRect(mon.WorkPos, mon.WorkPos + mon.WorkSize)) && "Monitor work bounds not setup properly. If you don't have work area information, just copy MainPos/MainSize into them.");
             IM_ASSERT(mon.DpiScale != 0.0f);
@@ -13484,7 +13485,8 @@ bool ImGui::DockNodeBeginAmendTabBar(ImGuiDockNode* node)
     Begin(node->HostWindow->Name);
     PushOverrideID(node->ID);
     bool ret = BeginTabBarEx(node->TabBar, node->TabBar->BarRect, node->TabBar->Flags, node);
-    IM_ASSERT(ret);
+    IM_UNUSED(ret);
+    IM_ASSERT(ret);    
     return true;
 }
 

imgui_widgets.cpp

@@ -7305,6 +7305,7 @@ static ImU32   ImGui::TabBarCalcTabID(ImGuiTabBar* tab_bar, const char* label, I
 {
     if (docked_window != NULL)
     {
+        IM_UNUSED(tab_bar);
         IM_ASSERT(tab_bar->Flags & ImGuiTabBarFlags_DockNode);
         ImGuiID id = ImHashStr(label);
         KeepAliveID(id);