This patch is based on Nutch-308.
This patch adds support for a maximum search time limit. After this time is exceeded, the search thread is stopped, partial results (if any) are returned and the total number of results is estimated.
This patch tries to minimize the overhead related to time-keeping by using a version of safe unsynchronized timer.
This was also discussed in an e-mail thread.
http://www.nabble.com/search-timeout-tf3410206.html#a9501029