Make all the easy updates. There are still quite a few to do, but in
doing these ones I can see that syntastic#makeprg#build() needs to
accept a few more options. Namely:
* "postargs" that appear after the filename
* "tail" that appears after everything - used for things like
redirecting output and piping to grep/sed/etc
* the filename itself - only the java checkers needed this since they
specify the directory of the file to check as well
There are still a few other things to do as well:
* remove the options from the checkers that are now provided by
syntastic#makeprg#build implicitly - i.e. the checker exe and args.
* also, we need to doc the above implicit checker options
* 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.
