Upgrade ImGui to latest docking versions 1.92.2 WIP

[reltham]

This commit in the imgui/docking branch:
ocornut/imgui@b431114

[reltham]

The check failure is because ImGui is expecting the "[[likely]]" feature to work based on reported version, but it's not with ubuntu clang.

// Hint for branch prediction
#if (defined(__cplusplus) && (__cplusplus >= 202002L)) || (defined(_MSVC_LANG) && (_MSVC_LANG >= 202002L))
#define IM_LIKELY   [[likely]]
#define IM_UNLIKELY [[unlikely]]
#else
#define IM_LIKELY
#define IM_UNLIKELY
#endif

Just going to have to modify the embedded imgui code to make this work, by commenting out the couple places using this.

[indigodarkwolf]

Strange that Clang++ choked on those options, but if that's the case then I don't see any real alternative but to comment out those hints. Fortunately, they're just hints and not critical to functionality.

Looks good, thanks for the PR!