gstreamer1.0-libav: enable gtk-doc again

Remove the broken piece of the API documentation template so the documentation
can be generated again.

(From OE-Core rev: 25a0d1b0b14a4fcd41ca08084a2f22db54dec58e)

Signed-off-by: Ross Burton <ross.burton@intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

meta/recipes-multimedia/gstreamer/gstreamer1.0-libav/gtkdoc-no-tree.patch

@@ -0,0 +1,35 @@
+Upstream-Status: Backport
+Signed-off-by: Ross Burton <ross.burton@intel.com>
+
+From 6f720cebe632d7dc187c6907857d67ce1f7313d6 Mon Sep 17 00:00:00 2001
+From: Ross Burton <ross.burton@intel.com>
+Date: Mon, 9 Sep 2019 22:48:49 +0100
+Subject: [PATCH] docs: don't include the type hierarchy
+
+gtk-doc can't generate a type hierarchy when scanning gst-libav, and gtk-doc
+1.30 onwards doesn't write a file if there is no type hierarchy (unlike previous
+releases, which wrote an empty file).  This results in the build failing with
+gtk-doc 1.30 onwards, so remove the type hierarchy section from the
+documentation as it doesn't serve any purpose.
+
+Fixes https://gitlab.freedesktop.org/gstreamer/gst-libav/issues/57
+---
+ docs/plugins/gst-libav-plugins-docs.sgml | 5 -----
+ 1 file changed, 5 deletions(-)
+
+diff --git a/docs/plugins/gst-libav-plugins-docs.sgml b/docs/plugins/gst-libav-plugins-docs.sgml
+index 75c68f4..f68d554 100644
+--- a/docs/plugins/gst-libav-plugins-docs.sgml
++++ b/docs/plugins/gst-libav-plugins-docs.sgml
+@@ -32,9 +32,4 @@
+     <title>gst-libav Plugins</title>
+     <xi:include href="xml/plugin-libav.xml" />
+   </chapter>
+-
+-  <chapter>
+-    <title>Object Hierarchy</title>
+-    <xi:include href="xml/tree_index.sgml" />
+-  </chapter>
+ </book>
+-- 
+2.22.0

meta/recipes-multimedia/gstreamer/gstreamer1.0-libav_1.16.0.bb

@@ -18,6 +18,7 @@ SRC_URI = "http://gstreamer.freedesktop.org/src/gst-libav/gst-libav-${PV}.tar.xz
            file://mips64_cpu_detection.patch \
            file://0001-configure-check-for-armv7ve-variant.patch \
            file://0001-fix-host-contamination.patch \
+           file://gtkdoc-no-tree.patch \
            "
 SRC_URI[md5sum] = "e3a201a45985ddc1327cd496046ca818"
 SRC_URI[sha256sum] = "dfac119043a9cfdcacd7acde77f674ab172cf2537b5812be52f49e9cddc53d9a"
@@ -28,11 +29,6 @@ DEPENDS = "gstreamer1.0 gstreamer1.0-plugins-base zlib bzip2 xz"
 
 inherit autotools pkgconfig upstream-version-is-even gtk-doc
 
-# Disable documentation for now as it is failing with gtk-doc 1.30:
-# gst-libav-plugins-docs.sgml:38: element include: XInclude error:
-# could not load xml/tree_index.sgml, and no fallback was found
-GTKDOC_ENABLED = "False"
-
 # CAUTION: Using the system libav is not recommended. Since the libav API is changing all the time,
 # compilation errors (and other, more subtle bugs) can happen. It is usually better to rely on the
 # libav copy included in the gst-libav package.