bldchn, set headerdir already in configure
introduce script gen_twsapi_config_h
generate and install new header twsapi_config.h
Merge branch 'twsapi_config.h' into next

* twsapi_config.h:
  generate and install new header twsapi_config.h
  introduce script gen_twsapi_config_h
  bldchn, set headerdir already in configure