Make SyntaxCheckers_*_GetLocList() dictionary functions.
Pass a reference to the current checker to syntastic#makeprg#build().
Add an optional 'redirect' argument to CreateAndRegisterChecker().
Change the sh checker to use the new dictionary functions.
Add a new registry method getLocListRaw() (needed for the sh checker).
update makeprg builder:
* it now accepts `fname`, `tail`, and `post_args` params.
* add some doc above syntastic#makeprg#build
* update a bunch of checkers to use the new params
Still have quite a few checkers that arent using makeprg#build.
Including all c* and a few other c-like checkers. And PHP.
Not to worried about c* as these checkers are complicated and probably
justify having their own logic to build makeprgs.
