Install doxygen doc for core c++ API if core library's installed.

CMakeLists.txt

@@ -702,6 +702,10 @@ endif(CMAKE_BUILD_TYPE MATCHES "Release")
 
 if(NOT EXCLUDE_FAUST_LIB_INSTALL)
 	install(TARGETS ${FAUST_TARGET} DESTINATION ${FAUST_INSTALL_LIB})
+	if(${BUILD_DOCUMENTATION})
+		string(REGEX REPLACE "(.*)/lib/.*" "\\1" DOC_INSTALL_PREFIX ${FAUST_INSTALL_LIB})
+		install(DIRECTORY "${PROJECT_BINARY_DIR}/doc/html" DESTINATION "${DOC_INSTALL_PREFIX}/share/faust/doc/")
+	endif()
 endif()