curl: Restore CMake-specific test and install code

Restore the LIBCURL test used previously within CMake.  Restore
installation of the 'COPYING' file with the CMake documentation.
curl: Restore CMake-specific zlib selection code
curl: Select file APIs on Windows

Choose small or large file support based on capabilities of compiler
and target platform.
curl: Restore CURL_CA_BUNDLE option

Restore the option added by commit v2.8.8~200^2 (Add CURL_CA_BUNDLE
option for SSL support, 2012-02-09).
curl: Restore installation of OpenSSL DLLs

Restore logic originally added by commit v2.8.10~119^2~1 (curl: Make
OpenSSL DLLs available to CMake on Windows, 2012-09-06).
TODO: Account for the commits below

$ git diff c5cbb318 7e0b0014
$ git log c5cbb318..7e0b0014

commit 7e0b0014664d7db64ab13a31d0624e5d61b4227c
Author: Ben Boeckel <ben.boeckel@kitware.com>
Date:   Fri Dec 17 11:41:30 2010 -0500

    Fix missed _POLL_EMUL_H_ and HAVE_POLL combo

commit 44fca8b51af2e198d2d2cc6a2ad5f18838f9d235
Author: Ben Boeckel <ben.boeckel@kitware.com>
Date:   Fri Dec 17 11:18:04 2010 -0500

    Check for poll when looking for _POLL_EMUL_H_

commit 8d3689072394e6410c766eac9a8b0cae598f6500
Author: Ben Boeckel <ben.boeckel@kitware.com>
Date:   Thu Dec 16 14:59:05 2010 -0500

    Use _POLL_EMUL_H_ instead of HAVE_POLL_FINE

    Headers define _POLL_EMUL_H_ if they are not in the kernel, so a try_run
    check for them is not necessary.