Add build target for doxygen

Includes documentation & dependency/call graphs

CMakeLists.txt

@@ -38,6 +38,26 @@ if(NOT MSVC AND NOT APPLE)
   find_package(Threads REQUIRED)
 endif()
 
+if (BUILD_DOCS)
+    find_package(Doxygen)
+
+    if (DOXYGEN_FOUND)
+        set(DOXYGEN_IN ${CMAKE_CURRENT_SOURCE_DIR}/cmake/Doxyfile.in)
+        set(DOXYGEN_OUT ${CMAKE_CURRENT_BINARY_DIR}/Doxyfile)
+
+        configure_file(${DOXYGEN_IN} ${DOXYGEN_OUT})
+
+        add_custom_target(docs ALL
+            COMMAND ${DOXYGEN_EXECUTABLE} ${DOXYGEN_OUT}
+            WORKING_DIRECTORY ${CMAKE_CURRENT_BINARY_DIR}
+            COMMENT "Generating API documentation with Doxygen"
+            VERBATIM )
+    else (DOXYGEN_FOUND)
+        message("Doxygen need to be installed to generate the doxygen documentation")
+    endif (DOXYGEN_FOUND)
+endif()
+
+
 #
 # LMDB
 #