Update to 1.7.1 to Support for large meshes

[inkydragon]

ref: ImDrawList: Support for large meshes (64k+ vertices) with 16-bits indices · Issue #2591 · ocornut/imgui

When I'm trying to draw some Fractals, It's easy to touch this limit.

[Gnimuc]

Hi, do you wanna make a PR? It should be as simple as to upgrade CImGuiBuilder to 1.71 and then regenerate wrappers using Clang.jl. I don't have time to do this until Sep. 15.(sorry, I'm quite addicted to WoW Classic.)

[Gnimuc]

Hi @inkydragon, I just pushed 1.72b to master. Sorry for the postpone, it took me one more week to level up my priest to 60. :P

[inkydragon]

There must be something wrong. When VtxBuffer.Size > 2^16, imgui still crashed. (use CImGui v1.72.0)

Assertion failed!

Program: C:\Users\woclass\AppData\Local\Julia-1.0.4\bin\julia.exe
File: /workspace/srcdir/cimgui/imgui/imgui.cpp, Line4030

Expression: draw_list->_VtxCurrentIdx < (1<<16) && "Too many vertices in ImDrawList using 6-bit indices. Read comment above"

Julia test code: Jui.jl/LargeMeshTest.jl

imgui test code: examples/example_glfw_opengl3 @ 1.72b + code snippet Issue #2591

[Gnimuc]

Oops, I forgot to update the backend, could you give #12 a try? @inkydragon