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
fix(emacs/lean-type): disable eldoc at flycheck error/warning

fix #204
feat(util/lean_path): normalize path in function dirname
feat(build): build standard library when building on Windows
feat(linja): remove drivename to fix problems with ninja

Remark: this is a little bit hackish, we should look for a better solution.