gstreamer: Allow libxml2 dependency to be configured.

gstreamer uses libxml2 to support the plugin registry and pipeline
load/save features. This change allows the user to build gstreamer without
libxml2 which saves a large amount of space on the target.

Closes #373.

Signed-off-by: Will Newton <will.newton@gmail.com>

package/multimedia/gstreamer/Config.in

@@ -1,8 +1,13 @@
 config BR2_PACKAGE_GSTREAMER
 	bool "gstreamer"
 	select BR2_PACKAGE_LIBGLIB2
-	select BR2_PACKAGE_LIBXML2
 	help
 	  GStreamer is an open source multimedia framework.
 
 	  http://gstreamer.freedesktop.org/
+
+config BR2_PACKAGE_GSTREAMER_LIBXML2
+	bool "require libxml2 for registry and load/save"
+	default y
+	select BR2_PACKAGE_LIBXML2
+	depends on BR2_PACKAGE_GSTREAMER

package/multimedia/gstreamer/gstreamer.mk

@@ -24,6 +24,14 @@ GSTREAMER_CONF_OPT = \
 		--disable-tests \
 		--disable-failing-tests
 
-GSTREAMER_DEPENDENCIES = libglib2 libxml2 host-pkgconfig
+GSTREAMER_DEPENDENCIES = libglib2 host-pkgconfig
+
+ifeq ($(BR2_PACKAGE_GSTREAMER_LIBXML2),y)
+GSTREAMER_DEPENDENCIES += libxml2
+else
+GSTREAMER_CONF_OPT += \
+	--disable-registry \
+	--disable-loadsave
+endif
 
 $(eval $(call AUTOTARGETS,package/multimedia,gstreamer))