Revert "Remove unused toolbar:text define"

This reverts commit 8ce70a7e.

It is true that toolbar:text shouldn't be used during LO
development, but it's still used by toolbar customization,
and such customized XMLs should still validate against the
dtd.

Change-Id: I95227a22ecc00a27f39591163ee09a78adde3168

framework/dtd/toolbar.dtd

@@ -29,6 +29,7 @@
 <!ATTLIST toolbar:toolbaritem
 	xlink:href CDATA #REQUIRED
 	toolbar:visible %boolean; "true"
+	toolbar:text CDATA #IMPLIED
 	toolbar:style CDATA #IMPLIED
 >
 <!ELEMENT toolbar:toolbarspace EMPTY>