Validate uses of OpTypeFunction. (#1867)

In the specification of `OpTypeFunction`, it says

> OpFunction is the only valid use of OpTypeFunction.

This commit add a check in the validator for this rule.

A test started to fail because the new check happens before the check
the test case is testing.  Updated the test case to still fail the
check it was suppose to fail originally.

http://crbug.com/874571