New function 'libxml-available-p'

* src/emacs.c (main): Call syms_of_xml unconditionally.
* src/lisp.h: Provide syms_of_xml prototype even when
HAVE_LIBXML2 is not defined.
* src/xml.c (Flibxml_available_p): New function, cloned from
Fgnutls_available_p.
(syms_of_xml): Provide Slibxml_available_p.

* doc/lispref/text.texi (Parsing HTML/XML): Document libxml-available-p.
(GnuTLS Cryptography, Format of GnuTLS Cryptography Inputs)
(Document Object Model): Fix indentation of the first paragraph.

* etc/NEWS (libxml-available-p): Mention libxml-available-p.

1 files changed, 8 insertions, 0 deletions

diff --git a/etc/NEWS b/etc/NEWS
index 9ae36bdb032..f9481405e4e 100644
--- a/etc/NEWS
+++ b/etc/NEWS
@@ -39,6 +39,14 @@ text.
 +++
 ** New function 'logcount' calculates an integer's Hamming weight.
 
++++
+** New function 'libxml-available-p'.
+This function returns non-nil if libxml support is both compiled in
+and available at run time.  Lisp programs should use this function to
+detect built-in libxml support, instead of testing for that
+indirectly, e.g., by checking that functions like
+'libxml-parse-html-region' return nil.
+
 
 * Editing Changes in Emacs 27.1