Handle multiline log messages
Handle multiline log messages

Some errors are of the form

file:line: explanation
l.line some latex code until the problem
    continuation of the description

We try to handle this multline structure correctly.

This closes #781.

James-Yu/LaTeX-Workshop,James-Yu/LaTeX-Workshop,James-Yu/LaTeX-Workshop,James-Yu/LaTeX-Workshop,James-Yu/LaTeX-Workshop