gif: fix build Had bit test wrong on transparency; no excuses.
gif: fix build
Had bit test wrong on transparency; no excuses.

R=nigeltao
CC=golang-dev
http://codereview.appspot.com/4526044

apparentlymart/golang,dsriram/golang,tv42/old-go,tv42/old-go,pombredanne/go-deleteme,tv42/old-go,ssrl/go,dsriram/golang,apparentlymart/golang,apparentlymart/golang,gnanderson/go,apparentlymart/golang,ssrl/go,tv42/old-go,pombredanne/go-deleteme,dsriram/golang,ssrl/go,apparentlymart/golang,pombredanne/go-deleteme,dsriram/golang,apparentlymart/golang,gnanderson/go,dsriram/golang,pombredanne/go-deleteme,tv42/old-go,apparentlymart/golang,ssrl/go,ssrl/go,gnanderson/go,dsriram/golang,pombredanne/go-deleteme,tv42/old-go,pombredanne/go-deleteme,ssrl/go,dsriram/golang,gnanderson/go,gnanderson/go,gnanderson/go,gnanderson/go,tv42/old-go,ssrl/go,pombredanne/go-deleteme