* README.checkout: Add description for libares
* configure.ac: Add check for libares
* doc/wget.texi: Add docs for the new options
* src/build_info.c.in: Add +/-cares for --version output
* src/host.c:
(merge_address_lists): New static function
(address_list_from_hostent): New static function
(wait_ares): New static function
(callback): New static function
(lookup_host): Add libares resolver code
* src/init.c: Add new options,
(cleanup): Add cleanup code
* src/main.c: Add global libares channel variable
(cmdline_option option_data): Add new options
(print_help): Add short descriptions
(main): Add libares init code
* src/options.h (struct options): Add option members
The new options allow to specify alternative DNS servers and
an alternate packet route for the resolver packets.
Wget has to built with libares, enabled at configure time by
./configure --with-cares.
