avoid once warnings when assigning EXPORT* vars

Normally, the EXPORT* vars will be immune to 'once' warnings.  In perl
5.25.6, EXPORT_TAGS lost its immunity to the warning.  While that will
most likely be fixed, we can just be safe and stop relying on having
that special cased.

Changes

@@ -1,6 +1,8 @@
 Revision history for {{$dist->name}}
 
 {{$NEXT}}
+  - Avoid possible warnings about special variables only being used once
+    (Graham Knop)
 
 0.001012  2016-08-23 11:18:21-07:00 America/Los_Angeles
   - Many small performance improvements (Peter Rabbitson)

lib/Sub/Exporter/Progressive.pm

@@ -18,6 +18,7 @@ sub import {
 
    my $full_exporter;
    no strict 'refs';
+   no warnings 'once';
    @{"${inner_target}::EXPORT_OK"} = @{$export_data->{exports}};
    @{"${inner_target}::EXPORT"} = @{$export_data->{defaults}};
    %{"${inner_target}::EXPORT_TAGS"} = %{$export_data->{tags}};