to return a linked lists of results. These were also modified to internally
use the ares_data memory struct and as such its result must be free'ed with
ares_free_data().

applications to free memory allocated and returned by some c-ares funtions.

getaddrinfo is fully thread safe on solaris versions which
implement the function even when h_errno is not a macro.

The h_errno macro test now only done on systems for which there
is no hard coded knowledge about getaddrinfo's thread safeness.

Remove files generated on previous buildconf/configure run

Remove enable-thread / disable-thread configure option. These were only placebo
options. The library is always built as thread safe as possible on every system.

Refactor how preprocessor symbol _THREAD_SAFE definition is done.

knowledge says the contrary or h_errno is not defined.

- Constantine Sapuntzakis reported that Darwin 6.0 a.k.a. MAC OS X 10.2
  and newer have a threadsafe getaddrinfo.

- Fix Dragonfly BSD triplet detection.

- In case the hard-coded knowledge says that getaddrinfo is threadsafe,
  an additional check is done to verify that h_errno is also defined.
  If h_errno isn't defined, we finally assume that it isn't threadsafe.
  Jamie Lokier provided the inspiration for this extra check.

Add some comments to better understand what the regex's pretend to achieve.

c-ares libraries in debug and release flavours.

Additionally each of the three sample programs is built against
each of the four possible c-ares libraries, generating all this
a total number of 12 executables and 4 libraries.

c-ares with --enable-curldebug uses memdebug.h from libcurl's lib subdirectory.

memdebug.h needs access to libcurl's setup.h from libcurl's lib subdirectory
and also needs access to libcurl's generated curl_config.h

Undo old temporary change once used for testing purposes