To achieve this, first new structure HeaderData is defined to hold
necessary data to perform header-related work. Then tool_header_cb now
receives HeaderData pointer as userdata. All header-related work
(currently, dumping header and Content-Disposition inspection) are done
in this callback function. HeaderData.outs->config is used to determine
whether each work is done.
Unit tests were also updated because after this change, curl code always
sets CURLOPT_HEADERFUNCTION and CURLOPT_HEADERDATA.
Tested with -O -J -D, -O -J -i and -O -J -D -i and all worked fine.
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.
