Debug: added DebugTextEncoding() to help diagnose between text encoding issues and font loading issues. Simplified code + extracted DebugNodeFontGlyph().

Helper to diagnose issues such as #4866, #3558, #3436, #2233, #1880, #1780, #905, #832, #762, #726, #609, #565, #307)

imgui.h

@@ -919,7 +919,7 @@ namespace ImGui
     IMGUI_API const char*   SaveIniSettingsToMemory(size_t* out_ini_size = NULL);               // return a zero-terminated string with the .ini data which you can save by your own mean. call when io.WantSaveIniSettings is set, then save data by your own mean and clear io.WantSaveIniSettings.
 
     // Debug Utilities
-    // - This is used by the IMGUI_CHECKVERSION() macro.
+    IMGUI_API void          DebugTextEncoding(const char* text);
     IMGUI_API bool          DebugCheckVersionAndDataLayout(const char* version_str, size_t sz_io, size_t sz_style, size_t sz_vec2, size_t sz_vec4, size_t sz_drawvert, size_t sz_drawidx); // This is called by IMGUI_CHECKVERSION() macro.
 
     // Memory Allocators