fix(doc/lean): typos
feat(frontends/lean): use coercions to function-class and sort-class in
function arguments, closes #203
fix(frontends/lean/pp): when formatting a coercion to function-class
that contains implicit arguments
fix(emacs/lean-flycheck): support windows

In windows, we need to first call python interpreter to call linja.
fix(emacs/lean-tags): support windows
fix(bin/linja): support windows

':' has a special meaning in build.ninja and has to be escaped. In
windows, ':' is used for drive names (i.e. c:).
refactor(bin/linja): clean up