Javascript and json have multiple syntax checkers that can be loaded.
Previously the logic to determine which checker to load was basically
copied and pasted in both. The `go` checker will soon have more
than one option too so remove the duplication by sticking the
common code in the core.
The js syntax checker was 4 checkers stuffed into 1 file. Now it is
broken down so that each checker is in its own file inside
syntax_checkers/javascript/ while syntax_checkers/javascript.vim just
determines which file to source.
Change the names of the global js checker config variables so that
they all start with "syntastic_javascript_". This is purely for
namespacing.
Remove some unneeded logic around the config variables too. Not sure how
it got in there, but it was more confusing than helpful without offering
any benefits...
Many of the syntax checkers were setting the 'bufnr' key for each
error manually and one was setting 'text' if it didnt exist too.
Add the 'defaults' option to SyntasticMake to set default values in the
returned error list - it only sets values if they are empty.
This was missing errors like this:
/tmp/foo.js:1:(-002) Error parsing file at token ")". Unable to check the rest of file.
The reason is because of the minus sign in front of the 002. It is using
%m to match that, which appears to only match positive numbers - so just
ignore the minus sign.
Add the g:syntastic_javascript_checker option so the user can specify
which javascript syntax checker to use. If none is specified then just
use the first syntax checker we find installed.
