#371 Changes in CMakeLists.txt for include/rt and include/rt/primitives

[Kalpit Thakkar]

There is no “primitives” directory in ${CMAKE_INSTALL_PREFIX}/include/brlcad/rt. Hence this needs changing in the CMakeLists.txt of ${BRLCAD_SOURCE_DIR}/include/rt and adding a CMakeLists.txt in ${BRLCAD_SOURCE_DIR}/include/rt/primitives.

[Sean Morrison]

Applied in r65086 and credited in our AUTHORS file, thanks!