godoc: use new index/suffixarray serialization code
godoc: use new index/suffixarray serialization code

When saving/restoring the fulltext index, the entire
respective suffixarray is now saved/restored (as opposed
to the indexed data only, and the suffixarray recreated).
This saves significant start-up time for large indexes,
at the cost of significantly larger index files.

R=r
CC=golang-dev
http://codereview.appspot.com/5037043

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