Correct name for linking opengl3_example
Correct name for linking opengl3_example

According to glfw offcial site, linking `libglfw.3.dylib` etc should
use `-lglfw`.

Changed this made the compilation on my Mac successfully.

wasikuss/imgui,ocornut/imgui,aimotive/imgui-glfw,Flix01/imgui,dougbinks/imgui,tom-seddon/imgui,seanmiddleditch/imgui,wflohry/imgui-addons,aimotive/imgui-glfw,nProtect/imgui,ggtucker/imgui,ocornut/imgui,cmaughan/imgui,thennequin/imgui,mikesart/imgui,cmaughan/imgui,seanmiddleditch/imgui,wasikuss/imgui,nProtect/imgui,ocornut/imgui,tom-seddon/imgui,elect86/imgui,thennequin/imgui,ggtucker/imgui,ggtucker/imgui,bkaradzic/imgui,wflohry/imgui-addons,bkaradzic/imgui,elect86/imgui,thevaber/imgui,mikesart/imgui,cmaughan/imgui,Pagghiu/imgui,dougbinks/imgui,burningreggae/imgui,bkaradzic/imgui,cmaughan/imgui,thevaber/imgui,nProtect/imgui,burningreggae/imgui,Flix01/imgui,Pagghiu/imgui,Flix01/imgui