Log Message:
curl: update to 7.58.0.

This release includes the following changes:

 o new libssh-powered SSH SCP/SFTP back-end
 o curl-config: add --ssl-backends [10]

This release includes the following bugfixes:

 o http2: fix incorrect trailer buffer size [40]
 o http: prevent custom Authorization headers in redirects [55]
 o travis: add boringssl build [1]
 o examples/xmlstream.c: don't switch off CURL_GLOBAL_SSL [2]
 o SSL: Avoid magic allocation of SSL backend specific data [3]
 o lib: don't export all symbols, just everything curl_* [4]
 o libssh2: send the correct CURLE error code on scp file not found
 o libssh2: return CURLE_UPLOAD_FAILED on failure to upload
 o openssl: enable pkcs12 in boringssl builds [5]
 o libssh2: remove dead code from SSH_SFTP_QUOTE [6]
 o sasl_getmesssage: make sure we have a long enough string to pass [7]
 o conncache: fix several lock issues [8]
 o threaded-shared-conn.c: new example
 o conncache: only allow multiplexing within same multi handle [9]
 o configure: check for netinet/in6.h [11]
 o URL: tolerate backslash after drive letter for FILE: [12]
 o openldap: add commented out debug possibilities [13]
 o include: get netinet/in.h before linux/tcp.h [14]
 o CONNECT: keep close connection flag in http_connect_state struct [15]
 o BINDINGS: another PostgreSQL client
 o curl: limit -# update frequency for unknown total size [16]
 o configure: add AX_CODE_COVERAGE only if using gcc [17]
 o curl.h: remove incorrect comment about ERRORBUFFER
 o openssl: improve data-pending check for https proxy [18]
 o curl: remove __EMX__ #ifdefs [19]
 o CURLOPT_PRIVATE.3: fix grammar [20]
 o sftp: allow quoted commands to use relative paths [21]
 o CURLOPT_DNS_CACHE_TIMEOUT.3: see also CURLOPT_RESOLVE
 o RESOLVE: output verbose text when trying to set a duplicate name
 o openssl: Disable file buffering for Win32 SSLKEYLOGFILE [22]
 o multi_done: prune DNS cache [23]
 o tests: update .gitignore for libtests
 o tests: mark data files as non-executable in git
 o CURLOPT_DNS_LOCAL_IP4.3: fixed the "SEE ALSO" to not self-reference
 o curl.1: documented two missing valid exit codes
 o curl.1: mention http:// and https:// as valid proxy prefixes
 o vtls: replaced getenv() with curl_getenv() [24]
 o setopt: less *or equal* than INT_MAX/1000 should be fine [25]
 o examples/smtp-mail.c: use separate defines for options and mail
 o curl: support >256 bytes warning messsages [26]
 o conncache: fix a return code
 o krb5: fix a potential access of uninitialized memory
 o rand: add a clang-analyzer work-around
 o CURLOPT_READFUNCTION.3: refer to argument with correct name [27]
 o brotli: allow compiling with version 0.6.0
 o content_encoding: rework zlib_inflate [28]
 o curl_easy_reset: release mime-related data [29]
 o examples/rtsp: fix error handling macros [30]
 o build-openssl.bat: Added support for VC15
 o build-wolfssl.bat: Added support for VC15
 o build: Added Visual Studio 2017 project files
 o winbuild: Added support for VC15
 o curl: Support size modifiers for --max-filesize [32]
 o examples/cacertinmem: ignore cert-already-exists error [33]
 o brotli: data at the end of content can be lost [34]
 o curl_version_info.3: call the argument 'age' [35]
 o openssl: fix memory leak of SSLKEYLOGFILE filename
 o build: remove HAVE_LIMITS_H check [36]
 o --mail-rcpt: fix short-text description
 o scripts: allow all perl scripts to be run directly [37]
 o progress: calculate transfer speed on milliseconds if possible [38]
 o system.h: check __LONG_MAX__ for defining curl_off_t [31]
 o easy: fix connection ownership in curl_easy_pause [39]
 o setopt: reintroduce non-static Curl_vsetopt() for OS400 support [41]
 o setopt: fix SSLVERSION to allow CURL_SSLVERSION_MAX_ values [42]
 o configure.ac: append extra linker flags instead of prepending them [43]
 o HTTP: bail out on negative Content-Length: values [44]
 o docs: comment about CURLE_READ_ERROR returned by curl_mime_filedata
 o mime: clone mime tree upon easy handle duplication [45]
 o openssl: enable SSLKEYLOGFILE support by default [46]
 o smtp/pop3/imap_get_message: decrease the data length too... [47]
 o CURLOPT_TCP_NODELAY.3: fix typo [48]
 o SMB: fix numeric constant suffix and variable types [49]
 o ftp-wildcard: fix matching an empty string with "*[^a]" [50]
 o curl_fnmatch: only allow 5 '*' sections in a single pattern
 o openssl: fix potential memory leak in SSLKEYLOGFILE logic
 o SSH: Fix state machine for ssh-agent authentication [51]
 o examples/url2file.c: add missing curl_global_cleanup() call [52]
 o http2: don't close connection when single transfer is stopped [53]
 o libcurl-env.3: first version
 o curl: progress bar refresh, get width using ioctl() [54]
 o CONNECT_TO: fail attempt to set an IPv6 numerical without IPv6 support [56]