Fix to SIMPLE_COLUMN resolution in HSQL parser

There is no fudge. The handling of SIMPLE_COLUMN is right here in this code block.
To the extent that I understand this change, I understand it as preventing a premature otherCol match that would cause this loop to quit before its intended otherCol is reached. The assert(false) in the fall-through from the for loop reassures that the intended otherCol will eventually appear. 

BTW, the prototypes entry for SIMPLE_COLUMN on line 1458 seems like a mistake (half-baked fudge?) -- the only effect of 'VoltXMLElement("simplecolumn")' is a missed chance to detect early a flaw in this loop's logic -- and that is only possible if asserts are disabled. The bogusness of "simplecolumn" is only detected much later in the AbstractParsedStmt code. MAYBE it used to get folded into the handling of "columnref" there?