Message files support now 4-bytes integer message numbers

2-byte .msg message number limitation was removed.

Before version 2.40, message files entries could only be defined with numbers in the range -32767 to 32767 (i.e. SMALLINT). This limitation is not longer true in 2.40: Message numbers can now be in the range -2147483648 to 2147483647 (i.e. INTEGER).