Roll-forward of c90c08ccc9 "Revert "Improvements to CMake buildsystem (#563)""
NEW:
* Replace CMAKE_SOURCE_DIR with CMAKE_CURRENT_SOURCE_DIR
Fixes#612 when yaml-cpp is used as a git submodule.
ORIGINAL:
* Move enable_testing() into proper place
* Added CMake's checks for C++11 standards
Raised minimal version of CMake to 3.1, since on old systems there no
decent compilers that supports c++11.
Closes#377.
* Externalize googletest project
Externalize gtest to avoid installation, fixes#539.
* Remove defined cmake_policies
CMP0012 - OLD marked as deprecated for >=cmake-3.1 and will be removed
CMP0015 - does not affect to build process
CMP0042 - already NEW for >=cmake-3.1
Fixes#505
* Fix compiling in Windows MSVC
* Move enable_testing() into proper place
* Added CMake's checks for C++11 standards
Raised minimal version of CMake to 3.1, since on old systems there no
decent compilers that supports c++11.
Closes#377.
* Externalize googletest project
Externalize gtest to avoid installation, fixes#539.
* Remove defined cmake_policies
CMP0012 - OLD marked as deprecated for >=cmake-3.1 and will be removed
CMP0015 - does not affect to build process
CMP0042 - already NEW for >=cmake-3.1
Fixes#505
* Fix compiling in Windows MSVC
It was incorrectly left at 0.6.0 when 0.6.1 was released, so this needs to be done to make it consistent between the tagged version and the CMake version.
Don't build tests if the confusingly named YAML_CPP_BUILD_TOOLS is ON.
Instead, add a new option that controls only if the tests are built.
(Also, default tests to OFF.)
Fix some virtual methods of NullEventHandler that were apparently
intended to overload base class methods, but did not. Add override
keyword to prevent these getting out of sync again.