[sort_segment_list] comments on optimization
attempted to speed up sort_segment_list::add
updated comment
removed commented out parts of previous code
[sortable_list] minor optimization - lbound and ubound are invariant during sort
Merge pull request #81 from gawrysz/merge_messages

Merge messages - optimization
Merge pull request #82 from gawrysz/optimization_sortable_list

[sortable_list] minor optimization