feat(frontends/lean): improve 'type mismatch' error position, and annotate 'have'-expressions

Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
feat(emacs): improve font highlighting in emacs mode

Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
fix(frontends/lean/pp): display private 'internal' names in a human readable way

Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
feat(frontends/lean/pp): add option for displaying internal names associated with private declarations

Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
fix(frontends/lean/decl_cmds): support for section declarations with implicit parameters, they must be tagged with '@' when creating aliases

Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
feat(frontends/lean/inductive_cmd): improve notation for declaring 'empty' inductive datatypes

Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
feat(frontends/lean/inductive_cmd): improve notation for declaring 'empty' inductive datatypes