Error with Jan 21, 2017 C++17 bugfix

[GeoffHadlington]

The bugfix to allow the use of the std::optional function from c++17 doesn't compile when building with c++17.
There is a hanging paren after the first #endif in optional.hpp, but in addition, the optional struct defines the bracket operator which is not defined on std::optional.
reply.cpp also didn't include the logger.hpp file containing the __CPP_REDIS_LOG macro.
Because of the std namespace override, the uses of the optional struct in the code needed to be replaced with optional_t.
Additionally, enableIf template needs to be added to the C++17 branch in optional.hpp.
Pull request incoming.

[GeoffHadlington]

#9
I believe this should resolve the problem satisfactorily for both c++17 and c++11

[EHadoux]

Hello, are you planning to merge into master today or later?

[GeoffHadlington]

Oh, sorry, I thought you were the maintainer. I don't know when he plans to merge it. :'D Sorry, I'm new to actually contributing to projects.

…

On Thu, Jan 24, 2019, 4:30 AM Emmanuel Hadoux ***@***.*** wrote: Hello, are you planning to merge into master today or later? — You are receiving this because you authored the thread. Reply to this email directly, view it on GitHub <#7 (comment)>, or mute the thread <https://github.com/notifications/unsubscribe-auth/AEAEzvyZx5DwDlppnE6pA2A2m7yImVvYks5vGZk6gaJpZM4aP0k6> .

[EHadoux]

Ahah that's fine don't worry, I'm compiling with your branch in the mean time.

[appkins]

I merged the changes into master. Thanks for the contribution!

[GeoffHadlington]

I'm an open source developer now! :p Very welcome.

…

On Fri, Mar 1, 2019, 2:40 PM appkins, ***@***.***> wrote: I merged the changes into master. Thanks for the contribution! — You are receiving this because you authored the thread. Reply to this email directly, view it on GitHub <#7 (comment)>, or mute the thread <https://github.com/notifications/unsubscribe-auth/AEAEzlTnG9xyxb_qUptCHorgKgNLFIJnks5vSZ5agaJpZM4aP0k6> .