[libgit2-glib] Do not require gtkdocize

[Jesse van den Kieboom <jessevdk src gnome org>]

commit 4ad0ada7dacae7754a1d852b9abdfff53e2e6dfc
Author: Jesse van den Kieboom <jkieboom esri com>
Date:   Wed Dec 30 17:42:30 2015 +0100

    Do not require gtkdocize

 autogen.sh |    6 +++++-
 1 files changed, 5 insertions(+), 1 deletions(-)
---
diff --git a/autogen.sh b/autogen.sh
index 8a7d049..1fdd8a5 100755
--- a/autogen.sh
+++ b/autogen.sh
@@ -22,7 +22,11 @@ if [ "$#" = 0 -a "x$NOCONFIGURE" = "x" ]; then
 fi
 
 aclocal --install || exit 1
-gtkdocize --copy || exit 1
+
+type gtkdocize >/dev/null 2>&1 && {
+       gtkdocize --copy || exit 1
+}
+
 autoreconf --verbose --force --install -Wno-portability || exit 1
 
 cd $olddir