Always give absolute paths to syntax checkers 'hdevtools' and 'hlint'

Especially for 'hdevtools' this results into a more robust behaviour,
because 'hdevtools' starts a background process and changing the
current directory doesn't affect the current directory of the background
process.
Merge pull request #1046 from dan-t/master

Always give absolute paths to syntax checkers 'hdevtools' and 'hlint'