bug: partition existence check hardcodes table name 'syslog', breaks syslog_removed and allows race condition

[somethingwithproof]

Description

In syslog_partition_create() (functions.php:192), the query that checks whether a partition already exists hardcodes table_name='syslog' regardless of the $table parameter:

$exists = syslog_db_fetch_row("SELECT *
    FROM `information_schema`.`partitions`
    WHERE table_schema='" . $syslogdb_default . "'
    AND partition_name='" . $cformat . "'
    AND table_name='syslog'       -- always 'syslog', ignores $table
    AND table_name='syslog'
    ORDER BY partition_ordinal_position");

syslog_partition_manage() calls this function for both syslog and syslog_removed. When called for syslog_removed:

• The check queries syslog instead of syslog_removed
• If syslog already has the partition, the check returns true and skips creation for syslog_removed — leaving it without a partition
• If syslog does not have the partition yet, the check returns false and creation proceeds correctly, but the inverse scenario also fails

There is also a race condition: if two poller processes check simultaneously before either creates the partition, both pass the check and both attempt ALTER TABLE ... REORGANIZE PARTITION, producing the "Duplicate partition name" error seen in #199 (particularly on DST fall-back nights when the process runs twice within the same clock hour).

Fix

1. Replace table_name='syslog' with table_name='$table' (or use a prepared statement).
2. Wrap the check-and-create in a GET_LOCK() / RELEASE_LOCK() to prevent the race.