Bug 6132: preference were case sensitive.

Signed-off-by: Chris Cormack <chrisc@catalyst.net.nz>
Signed-off-by: Paul Poulain <paul.poulain@biblibre.com>

C4/Context.pm

@@ -463,7 +463,7 @@ my %sysprefs;
 
 sub preference {
     my $self = shift;
-    my $var  = shift;                          # The system preference to return
+    my $var  = lc(shift);                          # The system preference to return
 
     if (exists $sysprefs{$var}) {
         return $sysprefs{$var};