Deprecate EffectiveStmtCtx.Current.original()

These methods are used to pass information to getOriginal(Definition)
methods, which themselves are deprecated for removal. Mirror that
decision so we do not end up exposing things we do not need.

Change-Id: Ib977818bc749bf722b9ce0c50664b0c0fda0a593
Signed-off-by: Robert Varga <robert.varga@pantheon.tech>
(cherry picked from commit 5442bfd168f34d386e872817ba5ce612d75c80d8)