It uses 'Note:' as a prefix as opposed to the common 'Warning:' to take
down the tone a bit.
It adds a warning for using -XHEAD on other methods becasue that may
lead to a hanging connection.
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.