Document the bundling approach.

debian/changelog

 haveged (1.9.1-7) UNRELEASED; urgency=medium
 
   * Add haveged-udeb, for use from the Debian Installer (See: #923675).
+  * Bundle the daemon and the library in haveged-udeb, since the daemon
+    is the only user of the libhavege.so.1 SONAME.
 
  -- Cyril Brulebois <kibi@debian.org>  Tue, 16 Apr 2019 22:25:19 +0000
 

debian/shlibs.local

+# No need to ship a separate libhavege1-udeb, so bundle the daemon and
+# the library in the same udeb (haveged-udeb), and let shlibs:Depends
+# computation know where libhavege.so.1 is shipped:
 udeb: libhavege 1 haveged-udeb