[4283] Updated INSTALL file to explicitly mention dependencies.

INSTALL

@@ -5,9 +5,11 @@ To then build from source:
     ./configure
     make
 
-For detailed installation directions, see the guide
-at doc/guide/kea-guide.txt or doc/guide/kea-guide.html.
+Kea depends on C++ compiler, make, libtool, boost libraries, log4cplus
+and one crypto library (either OpenSSL or Botan) for compilation.
+Optional backends (MySQL, PostgreSQL and Cassandra) have
+additional dependencies. For detailed installation directions, see the
+guide at doc/guide/kea-guide.txt or doc/guide/kea-guide.html.
 
 You can find user-contributed OS-specific build/installation
-instructions on the Kea wiki:
-http://kea.isc.org/wiki/SystemSpecificNotes
+instructions on the Kea wiki: http://kea.isc.org/wiki/Install