Bug 20074: Database revision to convert hidden to -5

The hidden value is used as a boolean in authority frameworks (in contrast
with biblio framework).
It is consistent to apply the same value (-5) to all non-zero values.

Test plan:
Check if you a have 0, 1 and 8 value in hidden somewhere.
Run the dbrev.
Verify that 1 and 8 are converted to -5.

Signed-off-by: Marcel de Rooy <m.de.rooy@rijksmuseum.nl>

Signed-off-by: Josef Moravec <josef.moravec@gmail.com>

Signed-off-by: Katrin Fischer <katrin.fischer.83@web.de>

Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>

installer/data/mysql/atomicupdate/bug20074.perl

@@ -0,0 +1,6 @@
+$DBversion = 'XXX';  # will be replaced by the RM
+if( CheckVersion( $DBversion ) ) {
+    $dbh->do(q|UPDATE auth_subfield_structure SET hidden=-5 WHERE hidden<>0|);
+    SetVersion( $DBversion );
+    print "Upgrade to $DBversion done (Bug 20074: Auth_subfield_structure changes hidden attribute)\n";
+}