Summary:
We minimize the number of "'sorry' used warning messages". We also
re-target the error to the main declaration. Example: foo._main ==> foo
We do not report for auxiliary declarations such as "_example" and
"foo.equations._eqn_1"
Get rid of the redundant error message "error : failed" for tactics.
We added "silent failures" in the tactic framework.
We do not store line/col information for tactics nested in notation
declarations. Before this commit, we would have tactics such
as (tactic.save_info line col) nested inside of notation declarations.
