The display of search results can now be changed. A slice of functions for displaying the results can now be provided. By default, three functions are provided to display documentation, source code, and textual results.
This makes it possible to replace them with equivalents that, say,
obtain search results from alternative source code search engines.
R=bradfitz, adg
CC=golang-codereviews
https://golang.org/cl/43470043
