Increase the size of the nfsheur hash table as pointed out by

Increase the size of the nfsheur hash table as pointed out by
Daniel Ellard and Margo Selzter in "NFS Tricks and Benchmarking Traps",
Proceedings of the 2003 Freenix Technical Conference.

         The two changes are to increase NUM_HEURISTIC, and increase
         the number of probes attempted before a search of the table
         is abandoned. You could make the max probes as high as
         NUM_HEURISTIC, if you want to trade time for space. My
         choice of constants is arbitrary; maybe they should be
         config options so people with really big servers can set
         it to whatever they like when they build their kernels.

Obtained from:  http://www.eecs.harvard.edu/~ellard/NFS
Approved by:  Dan Ellard