default_after_variadic.dd

Function parameters with default values are now allowed after variadic template parameters, and always take their default values. This allows using special tokens (eg __FILE__) after variadic parameters, which was previously impossible

Eg:
---
string log(T...)(T a, string file = __FILE__, int line = __LINE__)
{
  return text(file, ":", line, " ", a);
}

assert(log(10, "abc") == text(__FILE__, ":", __LINE__, " 10abc"));
---

This should be preferred to the previous workaround, which caused template bloat:
---
string log(string file = __FILE__, int line = __LINE__, T...)(T a);
---