build: Add agent-api.txt to the document files list
diff --git a/Makefile.am b/Makefile.am
index 023c9fb..1d4f1a5 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -69,7 +69,8 @@
 build_plugindir = $(plugindir)
 endif
 
-doc_files = doc/manager-api.txt doc/tag-api.txt doc/device-api.txt doc/adapter-api.txt
+doc_files = doc/manager-api.txt doc/tag-api.txt doc/device-api.txt \
+		doc/adapter-api.txt doc/agent-api.txt
 
 EXTRA_DIST = src/genbuiltin $(doc_files)