lua consolidate playlist_ functions

The way to call the playlist functions has changed
rb.playlist("option", var)
rb.playlist_add(filename) = becomes rb.playlist("add", filename)

added playlist.lua to the includes for conversion to old functions
if your script is broken by this change you simply add `require("playlist")`
to the top for the old functionality

added rb.playlist_tracks(dir, filename) to playlist.lua
this will allow you to add all tracks in a playlist.m3u8
to a lua table

Change-Id: I87fcc56be365d8495d214f069331b6ddbfbef1db

apps/plugins/lua/rocklib_aux.pl

@@ -76,6 +76,7 @@ my @forbidden_functions = ('^open$',
                            '^__.+$',
                            '^.+_(un)?cached$',
                            '^audio_.+$',
+                           'playlist_.+$',
                            '^round_value_to_list32$');
 
 my $rocklib = sprintf("%s/rocklib.c", $ARGV[0]);