Add the syntastic_stl_format flag and doc it under :help syntastic_stl_format. This allows the user to control what information is displayed in the syntastic statusline flag.
This is purely in the interests of keeping the code simple.
g:syntastic_auto_loc now has the following possible options: 1 or "full_auto" or "fully_auto" behaves as normal, closing the loclist when there are no errors and opening when there are errors. 2 or "semi_auto" will automatically close the loclist but _not_ automatically open it.
Move this variable out of syntastic.vim since we dont the core plugin shouldn't know any details of how the individual syntax checkers work.
this way we can add new expressions to errorformat to upgrade to the latest lessc output while preserving backwards compatibility
Looks like vim was expanding these to the filename of the buffer.