fix(frontends/lean/parser): uninit variable

Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
fix(emacs/lean-flycheck): fix eval-after-load to use library name
feat(library/standard): add classes for relations
feat(library/hott): begin porting Coq HoTT
refactor(library/standard): integrate hott with standard library
feat(library/standard/hott/path.lean): add theorems and clean up file
feat(library/standard): add sigma types and subtypes, make inhabited constructive
feat(library/standard/logic): add class nonempty
feat(library/standard/classes): add nonempty