MT#16235 make add_mapping work for both wheezy and jessie

+jessie: copied add_mapping without type coercion checks
 for recent versions of URI::NamespaceMap
+wheezy: fallback to SUPER::add_mapping of the older
 version of URI::NamespaceMap

Change-Id: I528bddfa55895486d29d161a24f96d89673e68df

lib/Data/HAL/URI/NamespaceMap.pm

@@ -24,6 +24,14 @@ sub uri {
     return;
 }
 
-sub add_mapping     { $_[0]->namespace_map->{$_[1]} = $_[2] }
+sub add_mapping {
+  my ($self,$name,$href) = @_;
+  my $map = $self->namespace_map;
+  if ($map) {
+    return $map->{$name} = $href;
+  } else {
+    return $self->SUPER::add_mapping($name,$href);
+  }
+}
 
 1;