Implement value printing for std::source_location

[Axel-Naumann]

Feature description

It'd be great to have std::source_location::current() print out more than (std::source_location) @0x...! Just needs a cling::printValue(const std::source_location *) overload.

Alternatives considered

No response

Additional context

No response

[devajithvs]

std::source_location was under the namespace experimental until recently. To use it under std:: namespace will require C++20

https://en.cppreference.com/w/cpp/utility/source_location