Add package for gtk_doc.

* Update docbook_xml_dtd to add older version aliases to the XML
catalog, as gtk_doc is looking for version 4.3.

build/jam/repositories/HaikuPorts/x86_gcc2

@@ -5,7 +5,7 @@ RemotePackageRepository HaikuPorts
 	# architecture "any" packages
 	be_book-2008_10_26-1
 	ca_root_certificates-2014_04_08-2
-	docbook_xml_dtd-4.5-1
+	docbook_xml_dtd-4.5-2
 	docbook_xsl_stylesheets-1.78.1-1
 	freedroidrpg_x86_data-0.15.1-1
 	openttd_gfx-0.4.7-1
@@ -106,6 +106,7 @@ RemotePackageRepository HaikuPorts
 	gperf-3.0.4-1
 	grep-2.14-5
 	groff-1.20.1-3
+	gtk_doc-1.20-1
 	guilib-1.2.1-1
 	guilib_devel-1.2.1-1
 	gutenprint-5.2.9-1
@@ -649,6 +650,7 @@ RemotePackageRepository HaikuPorts
 	gperf
 	grep
 	groff
+	gtk_doc
 	guilib
 	gutenprint
 	gyp