Use special function for appending to precmd_functions
Use special function for appending to precmd_functions

This way there appear no duplicates.
bartvm/powerline,IvanAli/powerline,blindFS/powerline,Luffin/powerline,lukw00/powerline,darac/powerline,cyrixhero/powerline,xfumihiro/powerline,Liangjianghao/powerline,EricSB/powerline,russellb/powerline,IvanAli/powerline,dragon788/powerline,russellb/powerline,lukw00/powerline,blindFS/powerline,bezhermoso/powerline,xfumihiro/powerline,prvnkumar/powerline,kenrachynski/powerline,darac/powerline,lukw00/powerline,cyrixhero/powerline,junix/powerline,S0lll0s/powerline,DoctorJellyface/powerline,darac/powerline,EricSB/powerline,areteix/powerline,cyrixhero/powerline,areteix/powerline,xxxhycl2010/powerline,junix/powerline,seanfisk/powerline,DoctorJellyface/powerline,Liangjianghao/powerline,russellb/powerline,QuLogic/powerline,dragon788/powerline,bezhermoso/powerline,IvanAli/powerline,junix/powerline,dragon788/powerline,QuLogic/powerline,DoctorJellyface/powerline,seanfisk/powerline,bezhermoso/powerline,Liangjianghao/powerline,S0lll0s/powerline,kenrachynski/powerline,xxxhycl2010/powerline,s0undt3ch/powerline,xfumihiro/powerline,bartvm/powerline,S0lll0s/powerline,Luffin/powerline,s0undt3ch/powerline,kenrachynski/powerline,areteix/powerline,EricSB/powerline,prvnkumar/powerline,QuLogic/powerline,prvnkumar/powerline,blindFS/powerline,s0undt3ch/powerline,xxxhycl2010/powerline,bartvm/powerline,Luffin/powerline,seanfisk/powerline