Load protocol-specific dictionaries if built with them.

The code in parser.c does static evaluation of things like

	if (DHCP-foo == ...)

When the DHCP dictionaries aren't loaded, that turns into static
comparison of two strings, which is always false.  Changing it to

	if (&DHCP-foo == ...)

makes it bail with an unknown attribute error.  This is because
we don't have pass2 fixups for that case.

src/main/mainconfig.c

@@ -788,6 +788,18 @@ int read_mainconfig(int reload)
 		return -1;
 	}
 
+	/*
+	 *	Try to load protocol-specific dictionaries.  It's OK
+	 *	if they don't exist.
+	 */
+#ifdef WITH_DHCP
+	dict_read(mainconfig.dictionary_dir, "dictionary.dhcp");
+#endif
+
+#ifdef WITH_VMPS
+	dict_read(mainconfig.dictionary_dir, "dictionary.vqp");
+#endif
+
 	/*
 	 *	It's OK if this one doesn't exist.
 	 */