swift234

[Sema] Suppress deprecation warnings inside implicit functions

This commit suppresses deprecation warnings for references to deprecated symbols
by climbing the DeclContext hierarchy to determine if the warning location is
inside an implicit function.

This is a quick fix to get rid of spurious warnings for deprecated enums whose
nil literal conformance is synthesized by the importer. These warnings would
occur even when user code made no apparent reference to the enum in question and
instead only referred to an imported class that itself referred to the enum in a
method signature. This quick fix intentionally drops some valid warnings
(for example, for a synthesized call to a deprecated initializer in a super
class). rdar://problem/20024980 tracks adding these special purpose warnings
back.

rdar://problem/20007266

Swift SVN r25720