To help assist with the detection of incorrect return codes, as per
commits ee23d13a79, 33b8960dc8 and aba98991a5, updated the operate
based functions to return CURLcode error codes.
Configuration files such as curl_config.h and all config-*.h no longer exist
nor are generated/copied into 'src' directory, now these only exist in 'lib'
directory from where curl tool sources uses them.
Additionally old src/setup.h has been refactored into src/tool_setup.h which
now pulls lib/setup.h
The possibility of a makefile needing an include path adjustment exists.