Previously tracing could be disabled and was not enabled by default in a
debug build. This isn't desirable but I had avoided fixing it because
enabling tracing in debug mode would be confusing because
``ENABLE_TRACING`` could be set to off but tracing would be enabled
anyway.
I have resolved this by renaming the option from ``ENABLE_TRACING`` to
``ENABLE_TRACING_FOR_NON_DEBUG``. The semantics of the optiona are now
that it will enable tracing in non-debug builds. I have also added code
to ensure that tracing is always enabled in debug builds.
Whilst I was here I also fixed how ``option()`` was being used. The
default value and comment were in the wrong order.
executables, include files and libraries. We use
``GNUInstallDirs.cmake`` which ships with CMake to do the difficult work
of setting a sensible default and setting up CMake cache variables.
These can be overriden when running CMake by setting the
``CMAKE_INSTALL_BINDIR``, ``CMAKE_INSTALL_INCLUDEDIR`` and
``CMAKE_INSTALL_LIBDIR`` cache variables.
The new ``BUILD_PYTHON_BINDINGS`` option (off by default) will enable
building the bindings and the new ``INSTALL_PYTHON_BINDINGS`` option
enables installing them.
