Wrong conversation from hex to dec of LSN

[ioguix]

Since 9.3, PostgreSQL uses 256 segments per WAL, not 255. That means a WAL size is 4GB, not 4GB-16MB.

In conséquence, the following conversation is false:

$max_lsn_dec = (hex('ff000000') * hex($wal_num)) + hex($wal_off);

it should be $max_lsn_dec = ( 4_1024_1024*1024 * hex($wal_num)) + hex($wal_off);

This bug should not have large impact in production, but it would be better to fix it.