godoc: enable qualified identifiers ("math.Sin") as query strings again
godoc: enable qualified identifiers ("math.Sin") as query strings again

A query string of the form ident.ident will be used both as a qualified
identifier for identifier search and as a regular expression.
Qualified identifier lookup got broken accidentally when introducing
regexp full text search. Cleaned up surrounding logic a bit.

R=rsc
CC=golang-dev
http://codereview.appspot.com/3984042
abustany/go,abustany/go,abustany/go,abustany/go,abustany/go,abustany/go,abustany/go