finer granularity control when generating src and lib makefiles.

Fix compiler warning: conditional expression is constant.

  though it failed to write a very small download to disk (done in a single
  fwrite call). It turned out to be because fwrite() returned success, but
  there was insufficient error-checking for the fclose() call which tricked
  curl to believe things were fine.

  CARES_HAVE_ARES_FREE_DATA. Current functionality of ares_free_data()
  makes it unnecessary.

  ares_addr6ttl in order to prevent name space pollution, along with
  necessary changes to code base and man pages.This change does not break
  ABI, there is no need to recompile existing applications. But existing
  applications using these structs with the old name will need source code
  adjustments when recompiled using c-ares 1.6.1.

  with the ones declared in ares.h

Make configure remove the curlbuild.h file included in distribution tarballs
for use by non-configure systems. As intended, configure would overwrite the
distributed one when doing in-tree builds. But VPATH builds would end having
two curlbuild.h files, one in the source tree and another in the build tree.

Make configure remove the ares_build.h file included in distribution tarballs.

Fix macro redefinition.

Fix name space pollution.

Allow using different extra import libraries for debug and release builds.

Add manifest stuff to msvc makefile

  closed by libcurl before the SSL lib were shutdown and they may write to its
  socket. Detected to at least happen with OpenSSL builds.

  CURLOPT_HTTPPROXYTUNNEL enabled over a proxy, a subsequent request using the
  same proxy with the tunnel option disabled would still wrongly re-use that
  previous connection and the outcome would only be badness.

  CARES_HAVE_ARES_FREE_DATA as an indication of function availability.

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.

calloc() and realloc() function calls.

  end up with entries that wouldn't time-out:

  1. Set up a first web server that redirects (307) to a http://server:port
     that's down
  2. Have curl connect to the first web server using curl multi

  After the curl_easy_cleanup call, there will be curl dns entries hanging
  around with in_use != 0.

  (http://curl.haxx.se/bug/view.cgi?id=2891591)

  its pkg-config file.  So -Wl stuff ended up in the .pc file, which is really
  bad, and breaks if there are multiple -Wl in our LDFLAGS (which are in
  PTXdist). bug #2893592 (http://curl.haxx.se/bug/view.cgi?id=2893592)