Add CMake option for install into moodycamel

Hi,
I tend to use your excellent queues in various placements.

I recently noticed that the concurrentqueue cmake build installs with the ".../moodycamel/" sub-directory.
However, this readerwriterqueue build does not have the moodycamel part.

I tend to root the include directories to work as:
#include <moodycamel/concurrentqueue.h>

As you wouldn't want to break existing code, any chance of a cmake option that would add the "moodycamel/" part into the readerwriterqueue install location?

Comienza comparando las configuraciones de instalación de CMake de readerwriterqueue y concurrentqueue para encontrar dónde se define el destino de los includes. Añade una opción para el prefijo de instalación de moodycamel/, conservando el valor predeterminado actual, y verifica después que los headers instalados admitan ambos layouts solicitados.