[devhelp] docs: document what #include is needed

[Sébastien Wilmet <swilmet src gnome org>]

commit 1fafb204d3b6219f50dc57ea94b2c7cbb1243f66
Author: Sébastien Wilmet <swilmet gnome org>
Date:   Sun May 7 18:50:36 2017 +0200

    docs: document what #include is needed

 docs/reference/devhelp-sections.txt |    2 ++
 1 files changed, 2 insertions(+), 0 deletions(-)
---
diff --git a/docs/reference/devhelp-sections.txt b/docs/reference/devhelp-sections.txt
index 806f33b..971bb29 100644
--- a/docs/reference/devhelp-sections.txt
+++ b/docs/reference/devhelp-sections.txt
@@ -1,3 +1,5 @@
+<INCLUDE>devhelp/devhelp.h</INCLUDE>
+
 <SECTION>
 <FILE>init</FILE>
 <TITLE>Initialization and Finalization</TITLE>