text/search: api proposal
text/search: api proposal

The implementation of this package will largely be based on
collate/colltab.Weighter.

Change-Id: Iecb35ee3e058669980315269d96a93a3a7db283f
Reviewed-on: https://go-review.googlesource.com/7927
Reviewed-by: Rob Pike <4dc7c9ec434ed06502767136789763ec11d2c4b7@golang.org>

cmars/tools,cmars/tools,npchp110/text,cmars/tools,cmars/tools,golang/text