Merge pull request #164 in ASAPO/asapo from feature-c-produder-api to develop

* commit '876c78ae': (22 commits)
  fix memleak
  update tests, add missing funcitons
  fix memleak
  fix tests
  fix memleak, test
  addef function asapo_create_message_header()
  fix build
  IngestModeFlags
  fix memory leak
  astyle
  fix bug
  fix build
  have type save handles in the c api
  get roid of handle_or_null, use template version
  use Send__ instead of Send for c api, assert that GenericRequestHeader structs match
  make common_c_glue really compile, fix some bugs
  add function to create a aspao-string from a c string
  add producer enum equality checks
  complete produce api
  add producer functions with wrapper
  ...