Change include dir for doc

Makefile

@@ -20,6 +20,7 @@ help:
 
 apidoc:
 	@$(call echo,Make $@)
+	@[ -e ./_install/include ] || $(MAKE) install
 	@$(SH) ./doc/build.sh
 
 opendoc: apidoc

doc/zh-Hans/api.doxyfile

@@ -800,7 +800,7 @@ INPUT                  = mainpage.md \
                          specs_ctrl.md \
                          spec_control_api.md \
                          spec_control_channel.md \
-                         ../../include
+                         ../../_install/include
 
 # This tag can be used to specify the character encoding of the source files
 # that doxygen parses. Internally doxygen uses the UTF-8 encoding. Doxygen uses