Integer overflow

[scumatteo]

In Optimizer.cc, line 85, you declare

const int nExpectedSize = (vpKFs.size())*vpMP.size();

but when the number of vpKF and vpMP is high for very large explorations, nExpectedSize results in overflow, and the next lines throw exceptions, because you're passing to the reserve method for the vectors a negative value.

Solved by declaring nExpectedSize as unsigned long.