Performance improvements

I've run cppcheck 1.62 over the library and test suite and fixed issues marked as potentially causing performance problems. This includes using prefix instead of postfix operators for iterators in for loops, removing assignments that aren't used before variables are assigned a new value, passing by const reference instead of by value, and initializing some variables in the test suite in the initializer list.

Also included is an interface change to the early exercise pricer. This change allows the boost::function1 objects used in path evaluation to receive multipath array state by reference, instead of by value.

The changes improve the test suite speed by about 3-5% on my system (~10m 20 seconds to ~9m 55s).