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.
The problem
---
Some people want to change the syntax checker args and/or executable.
Currently they have to create their own checker to do this.
Solution
---
Create a standard API for building a makeprg that allows users to set
global variables to override the exe or args.
This API is in use in the coffee and python/flake8 checkers - as
proofs of concept.
So, if the user wanted to change the args that get passed to `flake8`
they can now set `let g:syntastic_python_flake8_args="--foo --bar"` in
their vimrc. Similarly they could set `let
g:syntastic_python_flake8_exe='python foo.py'`
If the shebang contains -T, then the makeprg looks like:
perl '/path/to/efm_perl.pl' -c -w '/tmp/foo.pl' -Tc
Mods to syntastic#util#ParseMagicNumber
* rename it to ParseShebang (since this name seems more common)
* return an empty result set rather than 0 so callers dont have to
check if empty()
