gc: fix use of typekind array in error messages
gc: fix use of typekind array in error messages

Fixes issue 1697.

R=ken2
CC=golang-dev
http://codereview.appspot.com/4395045

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