Http Server: Makefile should depend on the code generation script

When changing the code generation script, the generated code should be
recompiled.

The generated code is now depends on the code generation script.

clean now cleans the auto generated files as well

Signed-off-by: Amnon Heiman <amnon@cloudius-systems.com>
Reviewed-by: Tomasz Grabiec <tgrabiec@gmail.com>
Signed-off-by: Pekka Enberg <penberg@cloudius-systems.com>