godoc: first cut at textual search
To enable use -fulltext flag; e.g.: godoc -v -fulltext -http=:7777
Enabling the fulltext index will use significantly more memory as
the text of all source code, the respective suffixarray, and the
file set data structure is kept in memory. At the moment there is
about 6Mb of source code (~1400 files) indexed under GOROOT.
Source code + suffix array together consume 5*(size of source) or
about 30Mb. The file set data structure consumes about 4b/src line.
By default only up to 5000 results are shown for now.
The presentation of the results needs tuning. In particular,
if a string is found, clicking on the respective file does not
highlight them, yet.
At the moment, only Go source files are indexed. Eventually,
the full text index should encompass other files as well.
R=rsc, adg
CC=golang-dev
https://golang.org/cl/
3182043