When adding a functional index on an expression that produces a row
value, an assertion would be hit. Row value expressions are already
disallowed for generated columns, and we try to do the same checking
for functional indexes as we do for generated columns. However, the checks
for generated columns are split into two; one for pre resolving and
one for post resolving. This patch moves the check for row value
expressions from the post check to the pre check as the information
is already available there.

Change-Id: I1a21ad29dd0b23125e2432a6305966bea4d27a85