Update to 7.58.0 - January 24 2018.

Changes:
	new libssh-powered SSH SCP/SFTP back-end
	curl-config: add --ssl-backends

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

Bug: N/A
Test: builds, boots, `vendor/google/tools/fake-ota on streaming` works
Change-Id: I91e0837f7b34a785f5bddb173262038dcaabdcda
558 files changed