Trim ImGui/Im prefixes from Dear ImGui enums

[eliasdaler]

I disabled trimming for implot due to ImGuiAxis/ImAxis clash (and also had some problems with some other things related to implot). Will try to do the same for implot after moving it to "implot" package later.

I thought about getting rid of prefixes somewhere on C++ generation stage, but I'd say it'll be harder to understand. Right now I needed some stuff in gengo which felt like hacks sometimes, but I think it's okay.

I might do the same for structs, but I'll think about it - it might take a bit more work to do because there's more code which references struct types.

[eliasdaler]

Any thoughts on this?

[AllenDang]

@eliasdaler May I ask you as collaborator of this project? Sent the invitation to you.

[AllenDang]

@eliasdaler Do you have time to create a pull request rule which will make sure every pull request at least could be built?

[eliasdaler]

May I ask you as collaborator of this project? Sent the invitation to you.

Yes. Thank you.

Do you have time to create a pull request rule which will make sure every pull request at least could be built?

Sure, will try to do it later this week.

[gucio321]

Looks good, just a few small points.

[gucio321]

and there are conflicts

[gucio321]

oh, @eliasdaler after merging #46 there are no more conflicts here!

[eliasdaler]

I'll get to this PR a bit later.

[gucio321]

ok, thank you!
I'm looking forward to see this PR merged! It'll radically chang (and enhance) API and I need it for AllenDang/giu#628 😄

[eliasdaler]

Okay, turns out trimming of ImPlot's "Im" prefix was needed after all... (because it conflicted with C function names)
@gucio321, please review again.

[gucio321]

Cool!