[planner] configure.ac: make GTK-Doc optional

[Alexandre Franke <afranke src gnome org>]

commit 84f9d481aa83d531e31c435014aeaad75e9f9e65
Author: Andrew Miloradovsky <andrew interpretmath pw>
Date:   Sun Feb 17 21:07:15 2019 +0000

    configure.ac: make GTK-Doc optional

 configure.ac | 4 ++++
 1 file changed, 4 insertions(+)
---
diff --git a/configure.ac b/configure.ac
index 10c7cd3..4088863 100644
--- a/configure.ac
+++ b/configure.ac
@@ -48,7 +48,11 @@ AM_GCONF_SOURCE_2
 dnl  -------------
 dnl | API docs    |--------------------------------------------
 dnl  -------------
+m4_ifdef([GTK_DOC_CHECK], [
 GTK_DOC_CHECK([1.14],[--flavour no-tmpl])
+],[
+AM_CONDITIONAL([ENABLE_GTK_DOC], false)
+])
 
 dnl NOTE: We need to use a separate automake conditional for this
 dnl       to make this work with the tarballs.