compiler: add result parameter names for inlinable functions

    
    An inlinable function body may need to refer to result parameters, so
    each result parameter needs a name.  We already give them all names in
    start_function (via create_result_variables).  Change the export data
    so that for an inlinable function we use those names for the function
    declaration's result parameters.
    
    Reviewed-on: https://go-review.googlesource.com/c/150070

From-SVN: r266532