build-sys: add 'man' entry in summary
diff --git a/configure.ac b/configure.ac
index da8cd57..2b02238 100644
--- a/configure.ac
+++ b/configure.ac
@@ -206,4 +206,5 @@
 	compression:		xz=${with_xz}  zlib=${with_zlib}
 	debug:			${enable_debug}
 	doc:			${enable_gtk_doc}
+	man:			${enable_manpages}
 ])