use Memoize to cache results of GetAuthorisedValues

Thanks to Frédéric Demians for the original impetus
to improve this function and for doing profiling.

Note that Memoize is a core module since at least 5.8.0.

Signed-off-by: Galen Charlton <galen.charlton@liblime.com>

C4/Koha.pm

@@ -22,6 +22,7 @@ use strict;
 use C4::Context;
 use C4::Output;
 use URI::Split qw(uri_split);
+use Memoize;
 
 use vars qw($VERSION @ISA @EXPORT $DEBUG);
 
@@ -62,6 +63,9 @@ BEGIN {
 	$DEBUG = 0;
 }
 
+# expensive functions
+memoize('GetAuthorisedValues');
+
 =head1 NAME
 
     C4::Koha - Perl Module containing convenience functions for Koha scripts