ImDrawList: merge draw command better, cases of multiple Begin/End gets merged properly
ImDrawList: merge draw command better, cases of multiple Begin/End gets merged properly

Psybrus/imgui,usagi/imguixx,shaggytwodope/imgui,seanmiddleditch/imgui,ggtucker/imgui,mikesart/imgui,aimotive/imgui-glfw,xunmengfeng/imgui,cmaughan/imgui,ggtucker/imgui,rxantos/imgui,tom-seddon/imgui,bkaradzic/imgui,GHF/imgui,thennequin/imgui,wangshijin/imgui,benoitjacquier/imgui,nProtect/imgui,tpoechtrager/imgui,thevaber/imgui,burningreggae/imgui,dougbinks/imgui,bkaradzic/imgui,thennequin/imgui,redblobgames/imgui,ocornut/imgui,Psybrus/imgui,nProtect/imgui,Flix01/imgui,nProtect/imgui,nmlgc/imgui,kylawl/imgui,xythobuz/imgui,rmoorman/imgui,ocornut/imgui,neshume/imgui,wangshijin/imgui,zho7611/imgui,bagobor/imgui,tom-seddon/imgui,kylawl/imgui,andresv/imgui,rmoorman/imgui,cmaughan/imgui,nmlgc/imgui,bagobor/imgui,twigletguy/imgui,ghassanpl/imgui,gyakoo/imgui,luiseduardohdbackup/imgui,wflohry/imgui-addons,redblobgames/imgui,benoitjacquier/imgui,ocornut/imgui,dougbinks/imgui,sakishum/imgui,seanmiddleditch/imgui,emoon/imgui,Flix01/imgui,thevaber/imgui,Pagghiu/imgui,zho7611/imgui,elect86/imgui,neshume/imgui,bkaradzic/imgui,cmaughan/imgui,burningreggae/imgui,cmaughan/imgui,andresv/imgui,tpoechtrager/imgui,rxantos/imgui,Pagghiu/imgui,gyakoo/imgui,xunmengfeng/imgui,ggtucker/imgui,wasikuss/imgui,Flix01/imgui,ghassanpl/imgui,sakishum/imgui,GHF/imgui,elect86/imgui,xythobuz/imgui,wasikuss/imgui,shaggytwodope/imgui,wflohry/imgui-addons,emoon/imgui,mikesart/imgui,usagi/imguixx,twigletguy/imgui,aimotive/imgui-glfw,luiseduardohdbackup/imgui