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.
Add explicit virtual dtor to GraphBuilderInterface. This avoids tripping
a -Wnon-virtual-dtor warning, and also ensures that the correct
(virtual) dtor is called if an instance is deleted via a pointer to the
base type.
Remove use of CMAKE_INSTALL_PREFIX when specifying install destinations.
It is preferred that install destinations are specified as relative
paths, not absolute paths. This is also needed to create relocatable
installs, and thus should fix#526.
Don't install LIBRARIES on Windows to `bin`; they belong in `lib`. (This
appears to have been done in a mistaken attempt to install the DLL's to
`bin`, which do need to be there, but RUNTIME DESTINATION already takes
care of this.)