build curl if system one is not supported

curl-7.36.0 with these files dropped:
 * {CMake,tests,docs,packages,src,vs,winbuild}/ CMakeLists.txt

conditionally link idn
drop check
add --disable-server
add ftw from freebsd
add -lm when linking against static yajl
(see isnan, isinf, etc in 3rdparty/yajl/src/yajl_gen.c)
check for tempfile success
use perl-JSON instead of ::XS
use nobody as default user
don't build ltdl if --without-included-ltdl is given
make filters link libsx for they use its symbols

Conflicts:
	client/src/filters/aes256/Makefile.am
	client/src/filters/aes256/Makefile.in
off_t is evil
fix crash on empty volume list (bb #448)
SSL certificate needs digitalSignature,keyEncipherment keyUsages too

OpenSSL doesn't check this, but NSS does
Fix sxi_rmdirs: FTW_D can be received in typeflag too
Support both OpenSSL and NSS (and curl built with either)

vcrypto.h: common API
openssl.c: openssl-specific code
nss.c: NSS-specific code
save certificate using CERTINFO API
fix sxi_set_operation leak
drop c99 decls
reverse the retriable/non-retriable failure logic
rework auth_begin
introduce sxc_set_tempdir