Make sure version lists are formed of numbers.
Set default reuse_loc_lists to 0.

Recent Vim versions have a bug related to setloclist(0, list, 'r'):

https://groups.google.com/forum/#!topic/vim_dev/t4ei24iwkiY

Avoid replacing loclists until the problem is solved.
More detailed logging.
Manual: clarification about g:syntastic_mode_map.  Minor cleanup.
Try to prevent g:syntastic_mode_map from being modified.
Bug fix: forgotten return.
Bug fix: SyntasticReset didn't really reset.