Add applications entry to .app.src file needed for relx.

src/mysql.app.src

@@ -19,5 +19,6 @@
 {application, mysql, [
     {description, "MySQL/OTP - Erlang MySQL client"},
     {vsn, "0.8.0"},
-    {modules, []}
+    {modules, []},
+    {applications, []}
 ]}.