Helper script efm_perl.pl is no longer needed, error formatting is now
done in a preprocess function.
g:syntastic_perl_interpreter is now a list. If set to a string,
the value is still used for backward compatibility, but a
deprecation warning is issued. There is also a buffer-scoped
b:syntastic_perl_interpreter.
Warnings are are now checked only if no errors are found.
Scenario:
- a C file is recognized as having filetype cpp
- run :SyntasticInfo
- run :setf c
- run :SyntasticInfo again
The only checker recognized will be oclint. The reason is, oclint is
registered as a c checker when called from cpp initialization, and that
prevents registering other c checkers when calling ':setf c'.
Solution: always initialize all checkers for a filetype.
