mudbox: convert most size_t back to mrs_natural
pitchextract: fix a numerical type mismatch
BeatTimeSink: fix a numerical type mismatch
CF_class: fix a numerical type mismatch
bextract: swap size_t for mrs_natural
kea: swap size_t for mrs_natural
mirex2008: swap size_t for mrs_natural
mirex2009: swap size_t for mrs_natural
pitchdtw: swap size_t for mrs_natural
pitchdtw: fix more numerical type mismatches
nextract: fix a numerical type mismatch
tempo: fix couple numerical type mismatches
unit test: RunningStatistics: explicitly convert mrs_natural to bool
AimSAI: include <algorithm> for std::max()
WekaData: fix usage of invalidated vector iterators
WekaSource: throw exception on failure to open file

Replace an assertion with an exception: the class does not handle failure
to open file, but assertion would not terminate program in release mode,
so rather use an exception.