Save replication comments for DROP TABLE.

<montywi> the task is the following:
<montywi> If one now do:
<montywi> DROP TABLE /* comment-for-replication */ t1,t2;
<montywi> When we write it to the binary log we remove the comment
<montywi> the task is to preserve the comment between drop table and the first table and write it to the replication log
<montywi> tungsten needs this to be able to know from which server the drop table originated.