Updated curl to 7.52.0. Security fixes.

Version 7.52.0 (20 Dec 2016)

Changes:

    nss: map CURL_SSLVERSION_DEFAULT to NSS default
    vtls: support TLS 1.3 via CURL_SSLVERSION_TLSv1_3
    curl: introduce the --tlsv1.3 option to force TLS 1.3
    curl: Add --retry-connrefused
    proxy: Support HTTPS proxy and SOCKS+HTTP(s)
    add CURLINFO_SCHEME, CURLINFO_PROTOCOL, and %{scheme}
    curl: add --fail-early

Bugfixes:

    CVE-2016-9586: printf floating point buffer overflow
    CVE-2016-9952: Win CE schannel cert wildcard matches too much
    CVE-2016-9953: Win CE schannel cert name out of buffer read
    msvc: removed a straggling reference to strequal.c
    winbuild: remove strcase.obj from curl build
    examples: bugfixed multi-uv.c
    configure: verify that compiler groks -Werror=partial-availability
    mbedtls: fix build with mbedtls versions < 2.4.0
    dist: add unit test CMakeLists.txt to the tarball
    curl -w: added more decimal digits to timing counters
    easy: Initialize info variables on easy init and duphandle
    cmake: disable poll for macOS
    http2: Don't send header fields prohibited by HTTP/2 spec
    ssh: check md5 fingerprints case insensitively (regression)
    openssl: initial TLS 1.3 adaptions
    curl_formadd.3: *_FILECONTENT and *_FILE need the file to be kept
    printf: fix ".*f" handling
    examples/fileupload.c: fclose the file as well
    SPNEGO: Fix memory leak when authentication fails
    realloc: use Curl_saferealloc to avoid common mistakes
    openssl: make sure to fail in the unlikely event that PRNG seeding fails
    URL-parser: for file://[host]/ URLs, the [host] must be localhost
    timeval: prefer time_t to hold seconds instead of long
    Curl_rand: fixed and moved to rand.c
    glob: fix [a-c] globbing regression
    darwinssl: fix SSL client certificate not found on MacOS Sierra
    curl.1: Clarify --dump-header only writes received headers
    http2: Fix address sanitizer memcpy warning
    http2: Use huge HTTP/2 windows
    connects: Don't mix unix domain sockets with regular ones
    url: Fix conn reuse for local ports and interfaces
    x509: Limit ASN.1 structure sizes to 256K
    checksrc: add more checks
    winbuild: add config option ENABLE_NGHTTP2
    http2: check nghttp2_session_set_local_window_size exists
    http2: Fix crashes when parent stream gets aborted
    CURLOPT_CONNECT_TO: Skip non-matching "connect-to" entries
    URL parser: reject non-numerical port numbers
    CONNECT: reject TE or CL in 2xx responses
    CONNECT: read responses one byte at a time
    curl: support zero-length argument strings in config files
    openssl: don't use OpenSSL's ERR_PACK
    curl.1: generated with the new man page system
    curl_easy_recv: Improve documentation and example program
    Curl_getconnectinfo: avoid checking if the connection is closed
    CIPHERS.md: attempt to document TLS cipher names


(wiz)