the scanner is now less eager about deprecations

When healing braces it isn't very useful to report deprecation warnings,
especially since this process is just simple context-free skimming, which
can't know about what positions can accept what identifiers.

Backport from https://github.com/scala/scala/pull/1807.
Original commit is https://github.com/scala/scala/commit/e5d34d70499504e085ddf957c1c818ffb63f4e8d.
changes the flags to not depend on partest

Due to some reason, partest always enables -deprecation. Since Paul has
just submitted a pull request, which removes this behavior, I'm updating
the flags to make sure this test works even after Paul's change.

Backport from https://github.com/scala/scala/pull/1807
Original commit is https://github.com/scala/scala/commit/2015ad3ebd833225e93ed19604760a6da2522bb1
Merge pull request #2036 from scalamacros/ticket/5716

[backport] the scanner is now less eager about deprecations