Revert r32811 -- regression in search.

Revert r32811 -- regression in search.
Caused search terms containing underscores to fail, as they had the underscores silently changed to spaces.
The means it's impossible to search for many programming terms in body text, say function names like 'str_replace'.

This was listed as a fix for bug 13616, but that seems to actually be about bad links in custom 'no article' text.
The links should be corrected instead.