COMP: Fix build of curl project against OpenSSL

On unix system, configuring curl passing OPENSSL_LIBRARIES did NOT have
the intended effect. Indeed, the FindOpenSSL.cmake provided by CMake is
doing call like "findlibrary(OPENSSL(CRYPTO|SSL)_LIBRARY ...)" ignoring
the value of OPENSSL_LIBRARIES. On MacOSX, this translated into a link
error related to "_ERR_remove_thread_state" symbol.

This commit updates curl external project so that the expected OpenSSL
libraries are found.

See 0001739

From: Jean-Christophe Fillion-Robin <jchris.fillionr@kitware.com>

git-svn-id: http://svn.slicer.org/Slicer4/trunk@22725 3bd1e089-480b-0410-8dfb-8563597acbee