CMake needs to specify -std=c++11 for older compilers about paho.mqtt.cpp

[fpagliughi]

Oh, BTW this was with CMake v2.8.12

Perhaps versions prior to CMake v3.1, don't honor the CMAKE_CXX_STANDARD setting?
set(CMAKE_CXX_STANDARD 11)

[fpagliughi]

Sure, if you want to keep looking at it.

[guilhermeferreira]

You are right. It seems a problem related to the combination of certain GCC and CMake versions. I'll check that.

[fpagliughi]

If this proves difficult, then don't worry about it. I don't want to spend too much time looking backwards. We can make a note of it in the build instructions and move on.

[fpagliughi]

This is likely the best we'll get without a lot of effort. I added instructions on how to upgrade the CMake on Ubuntu 14.04 to the README.md file. 4049f82

[guilhermeferreira]

I haven't seen this yet. Please, you might keep it opened. Right now I can't say how complicated it is.

[guilhermeferreira]

Hey @fpagliughi, check PR #89

[dontsovcmc]

It helps, thanks!