Disable SQL LIMIT optimisation during search

This patch is to make search work again after the new SQL optimisations,
by removing some of the optimisations when searching is used.
Optimisation of search is left for some future work.
The whole base is indeed transfered from MySQL to PHP, which is not
good.
Merge pull request #17 from Alkarex/SqlOptimisation

Disable SQL LIMIT optimisation during search