Search settings in ACP: Add information on minimum word size indexed when using Fulltext MySQL backend

The Fulltext Mysql search backend skips words with a number of characters fewer than the limit specified in the mysql cnf file. This can be confusing for an admin who is unaware of the mysql limit. I suggest adding the code specified in the attachment to let the admin know the minimum word size that will be indexed with Fulltext Mysql and how to change that size.