[gobject] Flesh out hb-gobject

Move it to new harfbuzz-gobject library.  Implement enums and
boxed types for object-types.  Still have to do boxed types for
value types.
diff --git a/docs/reference/harfbuzz-docs.xml b/docs/reference/harfbuzz-docs.xml
index 7062d6a..2731fab 100644
--- a/docs/reference/harfbuzz-docs.xml
+++ b/docs/reference/harfbuzz-docs.xml
@@ -26,6 +26,7 @@
     <xi:include href="xml/hb-shape.xml"/>
 
     <xi:include href="xml/hb-version.xml"/>
+    <xi:include href="xml/hb-deprecated.xml"/>
 
     <xi:include href="xml/hb-set.xml"/>
 
@@ -44,6 +45,8 @@
     <xi:include href="xml/hb-uniscribe.xml"/>
     <xi:include href="xml/hb-coretext.xml"/>
 
+    <xi:include href="xml/hb-gobject.xml"/>
+
   </chapter>
   <chapter id="object-tree">
     <title>Object Hierarchy</title>