Add support for built-in 'append'.
Add support for built-in 'append'.

thousandhigh/gocode,ghiden/gocode,suncycheng/gocode,artnez/gocode,beni55/gocode,MerlinDMC/gocode,suncycheng/gocode,mattn/gocode,artnez/gocode,mattn/gocode,mem/gocode,mdempsky/gocode,mem/gocode,lmh008/gocode,MerlinDMC/gocode,ghiden/gocode,fjl/gocode,syohex/gocode,mattn/gocode,louiseGrandjonc/gocode,toqueteos/LightTable-Go,louiseGrandjonc/gocode,artnez/gocode,mem/gocode,toqueteos/LightTable-Go,TheBB/gocode,kerr-huang/Gocode,kerr-huang/Gocode,syohex/gocode,lmh008/gocode,MerlinDMC/gocode,fjl/gocode,beni55/gocode,louiseGrandjonc/gocode,suncycheng/gocode,fjl/gocode,ghiden/gocode,lmh008/gocode,kerr-huang/Gocode,lmh008/gocode,thousandhigh/gocode,beni55/gocode,mattn/gocode,TheBB/gocode,beni55/gocode,MerlinDMC/gocode,TheBB/gocode,mdempsky/gocode,suncycheng/gocode,nsf/gocode,syohex/gocode,kerr-huang/Gocode,nsf/gocode,mem/gocode,mdempsky/gocode,thousandhigh/gocode,fjl/gocode,louiseGrandjonc/gocode,syohex/gocode,thousandhigh/gocode,nsf/gocode,nsf/gocode,artnez/gocode,ghiden/gocode,TheBB/gocode