[libcurl]: make SSL (now defaults to PolarSSL), zlib support and most options configurable

Signed-off-by: Imre Kaloz <kaloz@openwrt.org>



git-svn-id: svn://svn.openwrt.org/openwrt/packages@38456 3c298f89-4303-0410-b956-a3cf2f4a3e73