Lua: Allocine, grow buffer up to 500k

This seems a lot, but 65k definitively ain't enough for some
movies.
(cherry picked from commit 89dbfd782618074a2ee4122f0bead8a08917c805)
Signed-off-by: Jean-Philippe André <jpeg@videolan.org>

share/lua/extensions/allocine-fr.lua

@@ -278,7 +278,8 @@ function open_fiche(url)
 
     -- Open stream
     local s = vlc.stream(url)
-    local data = s:read(65535)
+    -- Read max 500k (Note: 65k is not enough for the average note)
+    local data = s:read(500000)
 
     -- Buffer & temp variables
     local first = nil