doc: Move Doxyfile into doc subdir

CMakeLists.txt

@@ -361,24 +361,7 @@ set(JSON_C_SOURCES
 include_directories(${PROJECT_SOURCE_DIR})
 include_directories(${PROJECT_BINARY_DIR})
 
-# generate doxygen documentation for json-c API
-
-find_package(Doxygen)
-option(BUILD_DOCUMENTATION "Create and install the HTML based API documentation(requires Doxygen)" ${DOXYGEN_FOUND})
-
-if (DOXYGEN_FOUND)
-
-	configure_file(${PROJECT_SOURCE_DIR}/Doxyfile.in
-	  ${PROJECT_BINARY_DIR}/Doxyfile)
-	message(STATUS "Written ${PROJECT_BINARY_DIR}/Doxyfile")
-
-	add_custom_target(doc
-	COMMAND ${DOXYGEN_EXECUTABLE} ${PROJECT_BINARY_DIR}/Doxyfile
-		WORKING_DIRECTORY ${PROJECT_BINARY_DIR})
-
-else (DOXYGEN_FOUND)
-	message("Warning: doxygen not found, the 'doc' target will not be included")
-endif(DOXYGEN_FOUND)
+add_subdirectory(doc)
 
 # uninstall
 add_custom_target(uninstall