Disallow check in a parameter default expression

Disallowing check in a default expression should apply to
default expressions generally, both in record fields and in function parameters.

Previously #886 disallowed it just for record fields, but it needs to be disallowed for function parameters also.

Fixes #1301.

Author: jclark

lang/spec.html

@@ -1819,10 +1819,9 @@ <h5>Record types</h5>
 href="#isolated_functions">isolated function</a>. The closure is evaluated to
 create a field value each time the default is used in the construction of a
 mapping value. The default value does not affect the type described by the type
-descriptor. It is a compile-time error if a default-expression in an
-individual-field-descriptor contains a checking-expr with a checking-keyword of
-<code>check</code>, i.e. if evaluation of the expression could complete abruptly
-with a check-fail.
+descriptor. It is a compile-time error if a default-expression
+contains a checking-expr with a checking-keyword of <code>check</code>,
+i.e. if evaluation of the expression could complete abruptly with a check-fail.
 </p>
 <p>
 A <code>record-type-inclusion</code> includes fields from a named record type.