don't display default value for variadic

[remicollet]

Running php --re standard:

Before:

    Function [ <internal:standard> function compact ] {

      - Parameters [2] {
        Parameter #0 [ <required> $var_name ]
        Parameter #1 [ <optional> ...$var_names = <default> ]
      }
      - Return [ array ]
    }

After:

    Function [ <internal:standard> function compact ] {

      - Parameters [2] {
        Parameter #0 [ <required> $var_name ]
        Parameter #1 [ <optional> ...$var_names ]
      }
      - Return [ array ]

And by consistency with zend_get_function_declaration which uses:

if (i >= required && !ZEND_ARG_IS_VARIADIC(arg_info)) {

[nikic]

Thanks!

[remicollet]

Applied in 91f47ee