update comments

git-svn-id: https://svn.r-project.org/R/trunk@73771 00db46b3-68df-0310-9c12-caf00c1e9a41

src/library/base/man/libcurlVersion.Rd

@@ -1,6 +1,6 @@
 % File src/library/base/man/curlVersion.Rd
 % Part of the R package, https://www.R-project.org
-% Copyright 2015 R Core Team
+% Copyright 2015-2017 R Core Team
 % Distributed under GPL 2 or later
 
 \name{libcurlVersion}
@@ -18,7 +18,7 @@ libcurlVersion()
   A character string, with value the \code{libcurl} version in use or
   \code{""} if none is.  If \code{libcurl} is available, has attributes
 
-  \item{ssl_version}{A character string naming the SSL implementation
+  \item{ssl_version}{A character string naming the SSL/TLS implementation
     and version, possibly \code{"none"}.  It is intended for the version
     of OpenSSL used, but not all implementations of \code{libcurl} use
     OpenSSL --- for example macOS reports \code{"SecureTranspart"}, its
@@ -32,6 +32,13 @@ libcurlVersion()
   \item{protocols}{A character vector of the names of supported
     protocols, also known as \sQuote{schemes} when part of a URL.}
 }
+\section{Warning}{
+  In late 2017 a \code{libcurl} installation was seen divided into two
+  libraries, \code{libcurl} and \code{libcurl-feature}, and the first
+  had been updated but not the second.  As the compiled function
+  recording the version was in the latter, the version reported by
+  \code{libcurlVersion} was misleading.
+}
 \seealso{
   \code{\link{extSoftVersion}} for versions of other third-party
   software.
@@ -41,10 +48,11 @@ libcurlVersion()
 
   \url{http://curl.haxx.se/docs/sslcerts.html} and
   \url{http://curl.haxx.se/docs/ssl-compared.html} for more details on
-  SSL versions.  Normally \code{libcurl} used with \R uses
-  SecureTransport on macOS, OpenSSL on Windows and GnuTLS, NSS or OpenSSL
-  on Unix-alikes.  (At the time of writing Debian-based Linuxen use
-  GnuTLS, RedHat-based ones use NSS.)
+  SSL versions (the current standard being known as TLS).  Normally
+  \code{libcurl} used with \R uses SecureTransport on macOS, OpenSSL on
+  Windows and GnuTLS, NSS or OpenSSL on Unix-alikes.  (At the time of
+  writing Debian-based Linuxen use GnuTLS and RedHat-based ones use NSS,
+  but it has been announced that Fedora 27 will switch to OpenSSL.)
 }
 \examples{
 libcurlVersion()