Adjustments to CMake Building

[scottfurry]

From CMake Docs( https://cmake.org/cmake/help/latest/variable/BUILD_SHARED_LIBS.html ),
BUILD_SHARED_LIBS may not be defined. This can result in printinfo.cmake outputing
variable without a value. A conditional is applied to ensure that some output is
provided to the user should variable not be defined.

Removed explicit C++ standard flag. Any setting user would add on the command
line would be replaced due to ordering. -std=c++0x would be last value added
to CMAKE_CXX_FLAGS and ultimately the one used by the compiler.

[danmar]

Removed explicit C++ standard flag.

ok.. how can it be provided by user if needed? I assume that is needed if an old gcc is used.

[scottfurry]

Two ways:

1. on the command line passing cmake ... -DCMAKE_CXX_STANDARD=11 ... if CMake version is > 3.1.

or 2) export CXXFLAGS="-std=c++11 before calling cmake

There is the set_target_properties() function available for older CMake (<3.1) but it would have to be set in multiple files as multiple targets are defined. Minimal CMake for project is starting to get old. I had to dig to find docs covering minimum required version.

[danmar]

ok thanks. I added some cmake instructions to the readme with the commit fef7bc5. Feel free to review that.

[scottfurry]

Project CMake specify minimum required version as 2.8.11. Hopefully people are at least updated to 3.x series and can use the flag identified. Again, alternative is to export CXXFLAGS='-std=c++11' if all else fails. Someone who has built software before should be aware of using export flag as a last resort.

Project Qt .pro files all have -std=c++11 explicitly set.

I think changes should cover most usage.
My mistake forgetting about updating documentation. Changes made look good.