Remove use of obsolete ImGui functions - v1.89

[Legulysse]

This PR contains a migration commit to allow imgui-sfml to be compiled with the flag IMGUI_DISABLE_OBSOLETE_FUNCTIONS.
Target imgui version : 1.89

Edit: this PR is tied to this ticket : #301

[ChrisThrasher]

Thanks! I need a little more time to figure out how I want to enforce this in CI but once I do that I can get this merged.

[Legulysse]

Nice !
To be clear, this update will not impact people already using 1.89, it will only make it available for people using the stricter compilation with the deprecation flag.

[ChrisThrasher]

Decided to make IMGUI_DISABLE_OBSOLETE_FUNCTIONS PUBLIC so that consumers of the ImGui-SFML CMake target also get that defined. This means that when they compile Imgui.h they don't have access to functions that were not compiled into their build of ImGui-SFML.

@Legulysse Let me know what you think

[Legulysse]

Seems safer this way to me ! And it allows the library and its users to move forward alongside imgui's future versions.
(you left a typo, using "obsolute" instead of "obsolete" in the cmake doc)

[ChrisThrasher]

Thanks for your help on this. I'll get this merged into master as well. I'm still not sure what to do about future ImGui versions which make even more things obsolete but we can hopefully figure something out. In the meantime I hope this makes your life a little easier.

[Legulysse]

@ChrisThrasher Thank you for your work !
I guess I should close the other PR I made ?
Dont hesitate if you want to discuss those concerns further on the associated issue, or if you want me to provide PRs for those other updates later on.