Fix DBL_MAX distances crashing neighbor_joining_buildtree
Fix DBL_MAX distances crashing neighbor_joining_buildtree

They were originally set to DBL_MAX because infinity is difficult to
handle right. But apparently that messes things up as well. So now
uncorrected distances over 0.75 are just set to 10000: larger than any
realistic distance but small enough to not have to worry about precision.

benedictpaten/sonLib,benedictpaten/sonLib,benedictpaten/sonLib,benedictpaten/sonLib,benedictpaten/sonLib