afb-binding-v3: Fix issues in includes

Fix 1: afb_api_v3_verbose doesn't exist

Fix 2: afb_api_vverbose isn't declared

Fix 3: Ensure implicit cast of "api" and "req"

  Using presupposed knowledge of internals of afb_api_t
  and afb_req_t is bad when dealing with implicit
  conversion in C++ and is generally not the way to
  go.

Change-Id: I2630faa5ea0ae315ca95e4fd6ed6ae1a0beb01a5
Signed-off-by: José Bollo <jose.bollo@iot.bzh>