Return non-nil from gnutls-available-p under GnuTLS 2.x

* doc/misc/emacs-gnutls.texi (Help For Users): Update the
documentation of 'gnutls-available-p'.

* etc/NEWS (GnuTLS): Mention the change in the value returned by
'gnutls-available-p'.

* src/gnutls.c (Fgnutls_available_p): Return non-nil when GnuTLS
2.x is available.  (Bug#29147)

1 files changed, 5 insertions, 1 deletions

diff --git a/doc/misc/emacs-gnutls.texi b/doc/misc/emacs-gnutls.texi
index 0ad48b0b9ec..92846a924c5 100644
--- a/doc/misc/emacs-gnutls.texi
+++ b/doc/misc/emacs-gnutls.texi
@@ -94,7 +94,11 @@ There's one way to find out if GnuTLS is available, by calling
 Zaretskii) in the same directory as Emacs, you should be OK.
 
 @defun gnutls-available-p
-This function returns @code{t} if GnuTLS is available in this instance of Emacs.
+This function returns non-@code{nil} if GnuTLS is available in this
+instance of Emacs, @code{nil} otherwise.  If GnuTLS is available, the
+value is a list of GnuTLS capabilities supported by the installed
+GnuTLS library, which depends on the library version.  The meaning of
+the capabilities is documented in the doc string of this function.
 @end defun
 
 Oh, but sometimes things go wrong.  Budgets aren't balanced,