Make checkstyle aware of message priorities.

Known bug: this breaks if the name of the file being checked contain one
of the characters <, >, ', ", &.
Add more knobs to the html/tidy checker.
Add hlint support
ghc-mod only does check phase
Remove hlint option from ghc-mod
Simplify errorformat
Compress whitespace
Add filetype maps for lhaskell and gentoo-metadata.

Remove checker for gentoo-metadata, since this is now an alias.
Merge pull request #741 from zenzike/master

Detangle ghc-mod and hlint
Ruby header file detection should work with all ruby versions
* Config module generates warning in ruby >= 1.9 that generates error
* Ruby >= 1.9 have different header file config name
Merge pull request #745 from MasterLambaster/ruby-detection

Make ruby c header detection work with all ruby versions
Add a SyntasticReset command.
Shell escaping is safer since commit a1e1108.
Replace lmake with equivalent system + lgetexpr.

It's now possible to deal with \0 characters in checkers' output.
Shell escaping is saner and safer.
SyntasticMake() has a new option 'preprocess'.
Checkers html/validator and eruby/ruby now use the new preprocess
option.  Auxilliary script validator_decode.awk is no longer needed.
Validator checker: check curl return status.
Undo most of the changes to eruby/ruby.

The new proprocess option is not useful here.
Merge branch 'fix_checkstyle' into preprocess
Fix checkstyle error levels. Closes #709.
Fix shell escaping.
Fix shellpipe expansion.