Simplify DEPRECATED / is DEPRECATED for now

Before, I was thinking of having sub DEPRECATED figure out what is was warning
for, with using callframe().  But this proved to be very fragile.  So instead,
sub DEPRECATED now just gets the old and new name, and the "is DEPRECATED"
trait adds a closure in the form of once block in an ENTER phaser for the
routine.  For this to work inside routines without explicit ENTER blocks,
the time that "finish_code_object" in Actions.nqp is called, must be changed.
But I'll leave that for tomorrow.

src/core/Cool.pm

@@ -105,12 +105,12 @@ my class Cool { # declared in BOOTSTRAP
     }
 
     method ucfirst() { # is DEPRECATED doesn't work in settings
-        once DEPRECATED('tc');
+        once DEPRECATED('Method Cool.ucfirst', 'tc');
         self.tc;
     }
 
     method capitalize() { # is DEPRECATED doesn't work in settings
-        once DEPRECATED('tclc');
+        once DEPRECATED('Method Cool.capitalize', 'tclc');
         self.Stringy.tclc;
     }
     method wordcase()   { self.Str.wordcase }
@@ -227,16 +227,16 @@ my class Cool { # declared in BOOTSTRAP
 Metamodel::ClassHOW.exclude_parent(Cool);
 
 sub ucfirst(Cool $s) { # is DEPRECATED doesn't work in settings
-    once DEPRECATED('tc');
+    once DEPRECATED("Sub 'ucfirst'", "'tc'");
     $s.tc;
 }
 proto sub capitalize($) { * }
 multi sub capitalize(Str:D $x) { # is DEPRECATED doesn't work in settings
-    once DEPRECATED('tclc');
+    once DEPRECATED("Sub 'capitalize'", "'tclc'");
     $x.tclc;
 }
 multi sub capitalize(Cool $x)  { # is DEPRECATED doesn't work in settings
-    once DEPRECATED('tclc');
+    once DEPRECATED("Sub 'capitalize'", "'tclc'");
     $x.Stringy.tclc;
 }
 

src/core/Str.pm

@@ -782,7 +782,7 @@ my class Str does Stringy { # declared in BOOTSTRAP
     }
 
     method capitalize(Str:D:) { # is DEPRECATED doesn't work in settings
-        once DEPRECATED('tclc');
+        once DEPRECATED('Method Str.capitalize', 'tclc');
         self.subst(:g, rx/\w+/, -> $_ { .Str.tclc });
     }
     method wordcase(Str:D: :&filter = &tclc, Mu :$where = True) {

src/core/core_epilogue.pm

@@ -1,6 +1,6 @@
 
-sub DEPRECATED ($changeto) {
-    warn "please change to $changeto";
+sub DEPRECATED ( $old, $new ) is hidden_from_backtrace {
+    warn "$old has been deprecated, please use $new instead";
 }
 
 # Re-parent meta-objects so they appear to be under Any.

src/core/traits.pm

@@ -94,7 +94,16 @@ multi trait_mod:<is>(Routine:D $r, :$default!) {
     $r does role { method default() { True } }
 }
 multi trait_mod:<is>(Routine:D $r, :$DEPRECATED!) {
-    $r.add_phaser( 'ENTER', -> { once DEPRECATED($DEPRECATED) } );
+    my $old = $r.WHAT ~~ Method
+#      ?? "Method {nqp::getattr($r,'Routine','$!package')}.{$r.name}"
+      ?? "Method '{$r.name}'"   # getattr for package fails
+      !! "Sub '{$r.name}'";
+    my $new = $DEPRECATED ~~ Bool
+      ?? "something else"
+      !! $DEPRECATED;
+    $r.add_phaser( 'ENTER', -> {
+        once DEPRECATED($old, $new);
+    } );
 }
 multi trait_mod:<is>(Routine:D $r, Mu :$inlinable!) {
     $r.set_inline_info(nqp::decont($inlinable));