Add some spec for "is DEPRECATED"

Author: lizmat

S02-bits.pod

@@ -4956,4 +4956,15 @@ The STD::Regex grammar also adds these:
     mod_internal:sym<P5>                     m:/ ... :P5 ... /
     quantifier:sym<*>                        /.*/
 
+=head1 Deprecations
+
+A language that doesn't evolve, is a dead language.  Constructs that
+seem like a good idea now, may turn out not to be such a good idea in the
+future.  Such constructs will thus need to be deprecated.  To mark a construct
+as being deprecated, one can add the "is DEPRECATED($alternative)" trait to
+a class, an attribute, or a sub / method.  During execution, this will cause
+the caller sites to be recorded without any warnings.  When execution finishes,
+a report should be printed to STDERR stating which deprecated features where
+called where.
+
 =for vim:set expandtab sw=4: