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'`
The output of flake8 is ambiguous as to whether results should be
interpreted as warnings or errors. I have changed it to assume errors to
match the python/pyflakes checker.
In future we may want to change this or add items to the errorformat for
some specific warnings if they are annoying.
This fixes#203.
* remove the public SyntasticHighlightErrors() function
* shift the above code into s:HighlightErrors(). This is called
automatically if g:syntastic_enable_highlighting is set
* to get the highlight regex we just look for a function called
Syntastic_<filetype>_GetHighlightRegex
* to force this function to be called, each error item must have the
'force_highlight_callback' key set
This code has one important functional change: now errors are *always*
highlighted if possible whereas previously they were only highlighted if
a call to SyntasticHighlightErrors was made.
